Before we talk about which domes we need to make sure you aren't wasting the space within your domes and building incorrectly.

• Your service slice is where people typically go wrong. In every dome you want a large triangle of grocer, infirmary, amphitheatre and a 1 tile fountain. This covers the core interests of social, relaxation, and shopping. You may additionally add services based on the needed interests of the specialisation of your dome but it's not strictly needed. Refer to below tables when considering how many service slices you need and what additional services you may add. Some would argue that a diner is better than an amphitheatre in your standard service slice, I'd agree for your initial dome simply due to the polymer cost of an amphitheatre but not after that. A 1 tile park isn't enough to cover relaxation needs, the dining interest is wasted while an amphitheatre gives you the needed relaxation, has no workers, and gives you luxury which your medics need and you have medics in every dome. The lack of needed workers easily offsets the polymer cost very quickly.
  
• Use the default living complex housing housing until you have hanging gardens, apartments aren't worth it until then. They're way too expensive for housing and cause comfort issues. You can actually just buy a second dome and fill it with the regular housing for cheaper than stuffing a single dome full of apartments. Don't bother with smart housing either, sanity is no issue with sufficient infirmaries.

Rough guideline:

This dome gets a lot of hate, wrongfully so as they're incredibly good for so many things. Yes it's the smallest, has no spire, and it's a pain for making service slices inside of if you need work buildings. But that still leaves you with so so many good things, especially when it's the only dome with no advanced material cost which is huge. They're basically free to build (unless on a low metal map).

Passageway links: look passages only go so far and before you get shuttles it's a nightmare if you want to build a dome far away from your initial domes. So chain 2-3 micro domes for basically no cost, then use them for one of the below bonus purposes.

Child domes: set your dome preferences to want kids and reject adults, then set all other domes to reject kids. Now all you need in your micro dome is a mix of schools, playgrounds, nurseries and decorations to fill in the gaps. Easy, you don't need a food service, just stick a food storage with desired food 5 outside. Playgrounds keep sanity and comfort so high that you don't need any services.

Senior domes: this time you don't care about their comfort, you actually want them to leave. So, all you need is housing, and maybe some parks if you're feeling nice or want to have some service overflow for neighbour domes. Don't put any worked services inside, and set the dome preferences to accept seniors and reject everyone else. Set every other dome to reject seniors.

Outdoor workspace: you don't need much to keep colonists reasonably happy, if you have some advanced metal pretty close to another dome just slap one of these down, give it housing, a grocer, park and diner. That's it you're done. To fill niche needs like gambling and drinking just let them take the minor penalty for using the neighbour dome. This is much much more efficient than building a larger dome for a minor thing. Feel free to slap down a polymer factory or something once the deposit runs out, or just salvage the dome, it was so cheap to build it's no big deal to remove it.

Power dome: you can put your solar panels inside them and they won't shut down in dust storms. Or put your stirling generators inside and leave them open without having to worry about dust. Solar panels also have a lower maintenance cost inside of domes and you can turn the dome itself off and pay no maintenance on it. I'm not sure there's ever much of a need to build domes just for putting power inside of them, but if you've got the dome sat there with space free or you don't know what to do with it as you were just linking passages then here's an option for you.

Lots of people seem to proclaim this dome as the best starter dome as you don't have spires early on, so who cares about basic domes right? It's easy to see why this is the initial conclusion when it's the largest dome you have at the start and that has some convenience to it.

However lets do a simple cost breakdown here. While the barrel dome will save you minor amounts of water and power compared to the basic dome for the space you get (both use 1 water 15 power), it's going to cost you upfront double the polymer which is very precious early on, on top of that the maintenance costs you polymer! Even though water/power is semi-precious, I can't see why you'd ever build this just for the slight water/power efficiency difference. Just build a second basic dome if you really feel it doesn't have enough space for what you're doing with it, then you get more space than the barrel dome for the same polymer cost and still no polymer maintenance cost. On top of that you can easily convert the basic domes into something helpful via their spires slots later.

If you want to argue that the water cost savings are more important than the polymer saving anyway, well the cost of a moisture vaporator is only 5 polymers and has no polymer maintenance, and water extractors are cheap enough too. So with that factored in it still isn't even close to enough to offset the higher polymer cost of the barrel dome.

Yes you could argue that the basic domes don't have enough space for all of the services as well as housing and workplaces, and I'd argue that that doesn't even come close to offsetting the huge cost difference. Especially when you're not going to want to be buying the expensive services at this point of the game anyway so you don't need that extra space for the services. Don't be so afraid to build wider by having a second basic dome sooner than you normally would vs buying a barrel dome. You don't need to shove everything in your starter dome.

And for those who use barrel domes for their child domes and claim that's a perfectly fine thing to convert it into, I have the same problem with you there. Compare the cost to the micro dome and the barrel dome is outrageously expensive. You really don't need to shove absolutely everything into a single dome I promise. Just build two micro domes.

The caveat to my beat down on using barrel domes is if you're playing on a low metal map. I'll give it to barrel domes that they are by far the most metal efficient dome for space, that's just never been something I've had to worry about as metal is normally abundant.

It's the main dome you start with, so it's going to be where you set up your initial colony most likely unless you're rushing for the milestone with a micro dome. If you have farms already, great just start it out with food production, if not I'd recommend skipping hydroponics and simply ordering all of your food in. That is unless you only have a single rocket, in which case you can't spare the rocket for constant food delivery. I like to go all in on just exporting rare metal with my first dome if not going for farms, just easy profit, no way to go wrong here.

You'll be using this dome for basically everything until you get medium domes. Technically for the space you get the micro dome is better cost unless you're struggling for water/metal, however due to the penalty of working in other domes and using services in other domes you don't want to be using the micro dome for most things. Once you have medium dome's you'll still want to be using the basic dome for your education dome.

Education dome: Why use the basic dome for this you ask, well it's because this is all about the sanatorium and you need lots of those. The basic dome is the cheapest dome you can fit a spire in and that's all that matters here.You'll be sticking the standard housing, security, medical, and service buildings in here along with the sanatorium and martian university.

Cloning vat spire dome: Same logic as the previous point, this is the cheapest dome which fits a spire which is what we want here. If you were fortunate enough to get the cloning vat spire, this is where you're putting it. If you really need more people early on that you can't get from earth (looking at you Japan) then you're going to need a dome or two with dedicated cloning vats for the spire. You don't want to ruin another dome with a cloning vat where they really need a garden.

Renegade dome: Doesn't really matter which dome you use for this, but hey I'll throw it in here because I like to put sanatoriums in mine so the basic dome works great for the same reason as the education dome. They tend to be renegades due to flaws after all so sanatoriums are nice. Plop one of these domes wherever, throw a fungal farm, resource extractor and polymer factory outside of it so all of the specialists can be helpful. Stuff it full of lots of security stations.

Alternative child dome: if you've got the school spire then congratz, your kids have been upgraded from micro domes to basic domes.

This gives you 9 large triangles compared to the medium dome's 12 (+3 single slots).

So 3:4~ in space. Interestingly that's the same as the cost ratio in polymer; 15 (1.5 maint) vs 20 (2 maint). The same goes for water and o2. The medium dome is slightly cheaper in metal and concrete for the space and the triagon is slightly cheaper in power. We don't really care about either of those costs as they're so minor.

So basically the medium and triagon dome are comparable for the cost of space. The medium is slightly better so I'd always use that but it doesn't really matter if you want to use the triagon instead. If you're playing in a cold zone the triagon fits subsurface heaters better around it but that's the only difference that would make you consistently use it. Typically the cost/space gets worse as the space gets larger, however the triagon has slightly worse cost/space compared to the medium with lower space. So yeah just generally a pretty bad dome but it's not such a huge cost difference that it's unusable or anything.

This is your bread and butter dome. It fits all of the services and housing you need while having the right amount of space left for other buildings to work in. It's the most cost efficient dome which can achieve that.

Farming: obviously when you have the water reclamation system spire you want it to be helping the water costs for as many farms as possible.

Everything else: I mean come on what did you expect me to say here. This is the most cost efficient dome which has enough space to fit everything you need. If you aren't making a farming dome then you're going to be using the hanging gardens 90% of the time as the comfort boost is absolutely insane. Don't talk to me about using the medical center in a medium dome, if you're having sanity problems just put down another infirmary, they're cheap and take up very little space. The hanging gardens give a crazy boost to comfort that otherwise you just aren't getting without spending a lot of resources and space on service buildings. The niche of the medical center spire is for if your dome is driving earthborns insane with all outdoor work, on night shifts, with heavy workloads, and you haven't researched anything to help sanity. Even then I'm not convinced you need it but I see the use, judge it case by case as the hanging gardens are water expensive. While we're talking about spires, also don't use the arcology spire. Their only niche to fill is if you've screwed up and really need more housing in a dome that doesn't have enough space left, they aren't something you should be planning to use. The hanging gardens are actually better for housing than the arcology spire is as you can keep people happy while cramming them in apartments. If you're having housing issues, before you put down an arcology spire check that you don't have a bunch of old people filling up your houses.

Fertility dome: Okay fine I lied there is another time you want to use the medical center spire. If you have the upgrade for higher fertility with the medical center spire you can make a dome just for breeding if you're in dire need of more people, filter the dome for sexy trait, make sure to check how many sexy people are in your colony before deciding if you want to do this. Still better to just have a cloning vat though but you may not have it, and this can actually go in any dome size you like but sure medium works.

Ew.

Literally worse than the medium dome in nearly every way. The mega trigon gets 3 medium spaces that the medium dome doesn't get, however that isn't anywhere near enough to make up for the huge increase in cost.

However, it does have a larger area than even the mega dome so it's pretty good for getting triple science boosts within the range of one dome or similar. Unfortunately I end up using this dome most games just to get the extra vistas or research sites in range

The same points I spoke about for the medium dome keep applying for the most part, the mega dome is more efficient for farming in terms of the water reclamation spire's applying to more farms. But the Medium domes actually are much more efficient for space to cost though and allow you to fit everything in just fine. Mega gets double the space but it's between 2x-5x the cost of the medium dome in various resources. You're also very able to overwhelm the garden spire and even in farming's case with no population application on the spire, the cost isn't worth the space and a medium works better. You're probably better off continuing to use medium domes really as you can easily fit all of the services you need into medium, but the appeal of spending a chunk more for more space to play around with is appealing even with worse efficiency. And really do you actually care about efficiency by the point you have mega domes? No of course not.

Yeah this is pretty bad for most things compared to the mega dome, you probably don't need the extra comfort bump as the hanging gardens in your mega dome has it covered just fine. This wonder is really a vanity project, you don't really need it.

However hey the bonus comfort will help if you want a huge birthing dome. For maximum efficiency birthing you want 100 comfort permanently and this helps with that. If you have the the holographic scanner tech then throw in the medical center spire for more births. And of course filter for sexy people

Okay you lucky duck you got one of the dome breakthroughs that lets you have a dome with two spires in it. Fine fine go nuts, have fun kids. They're still not as efficient as the medium dome for space even with the extra spire, they cost wayyyy more than the medium for only a little more space and the extra spire. Weirdly they're more water/o2 efficient than the medium but that's it. But being able to put two spires in one dome can be pretty damn strong so who cares if it's more expensive. Really, I'm not sure we even actually care about the cost by the point you have the mega or breakthrough domes.

You can do fun things like using the network node spire with the hanging gardens at the same time in your research domes. Or hanging gardens with school. Or hanging gardens with sanatariums. Huh it's almost like hanging gardens are OP or something?

You don't want to use these for farms as you don't need the hanging gardens comfort boost, you have a boost from the farms themselves anyway and you're better off with the mega dome for more space to apply the water savings from the water reclamation spire to.