Welcome to the world of Lethis! I've been playing the city building games by Impressions for over 15 years and got pretty good at it over the years, although I prefer to play them on a lower difficulty to relax. Still some players found it difficult to get the best out of their city (*cough* TotalBiscuit *cough*), so I wrote this guide with the most effective way I found to build a city.
It requires some space, so it is not suitable in all campaign missions. But the layout can easily be modified without losing too much by just shortening it and placing buildings where space is left.

Just to get this out of the way, optimizing industries is pretty easy. Keep the distances between the buildings small and you're good.
On limiting factor is steam, since the pipes cannot be built across water, so buildings like Automaton factories which need direct access have to be build next to your steam condensator. With others it is not that a big deal, just build a storage house in the near vicinity and set Steam to "get". But be careful and limit the amout or the storage will be filled with steam.

Being a city builder in the style of the classic Impressions games, I found the most effective way to build a city is in blocks. I had to change it up a bit for Lethis, but more about that later.

The basic structure is pretty simple: build nine houses length, than a road, the sort of a donut block with 3x9 houses, another road and nine more houses. I found that the patrolling workers will always walk a full circle, with a longer structure they have a chance to turn around and miss half the houses, depending on where they originate.
Top and bottom are reserved for buildings to satisfy the needs of the citizens.

Why this layout?
A patrolling worker will walk a certain distance from his/her building, then check paths back and choose the shortest one. With the proposed layout, the distance back by walking the rest of the path will be shorter than turning around. The maximum distance varies among buildings but here, they are all covered.
Furthermore, if a patrolling worker encounters an intersection, he/she will randomly chose a direction to go, making them unpredictable and coverage of services will suffer. By not building any intersections (road blocks seal off a road for patrolling workers), they don't get a choice and will patrol in the circle that is the building block


Requirements: none
Citzens: 3 per House, 114 in total

the only real requirement here is a Maintenance building to make sure the tents don't fall apart. A tax collector can be built if you have spare workers, which is most likely not the case if this is your first block of worker buildings. At later ones build one immediatly.


Requirements: Water
Citzens: 6 per House, in total 228
Only water is requiered for the first house expansion. Build a Well and wait until the worker has reached every house.


Requirements: water, one type of food, attractiveness
Citzens: 9 per house, in total 342

First important part: the Shop is a 3x3-building, so build it on the edge of a block to save space and make any other adjacend road unpassable for the patrolling worker with road blocks (workers with a destination are not affected by them). Most other buildings needed are only 2x2 which is the same size as a worker house. Some houses in the middle will probably not expand due to the lack of attractiveness in the neighborhood, which is very important to the citizens of Lethis (at least compared to their counterparts in the Impressions' classics). I left the space in the middle to build some 2x2 decorations, which are enough for now. It doesn't matter which decoration you pick as all of the same size have the same effect.


Requirements: water, one type of food, attractiveness, washhouse.
Citzens: 13 per House, in total 494

Nothing special, just build a washhouse, which is 2x4 in size. Houses on the edge will not expand due to attractiveness. To solve it build some small decorations next to them or, as I prefer, 3x3 at both edges of the block - higher level houses need more attrativeness and the 3x3 decorations have a higher range of increasing the attractiveness. Only go for the smaller ones if you lack money. But by now you should have enough excess workers to build a Townhall and Tax Collector.
Also, at this stage houses can get haunted. If they are not exorcized regularly, they will stay at level 4.


Requirements: water, one type of food, attractiveness, washhouse, alcohol, excorcist
Citzens: 17 per House, in total 646

Brining alcohol to the citizens is a no brainer, since it is delivered from the Shop. Put up a productions chain of your choice (or availability) and wait. Just make sure that a storage house is in the vicinity.


Requirements: water, one type of food, attractiveness, washhouse, alcohol, exorcist, theater
Citzens: 21 per House, in total 798

Citizens now want access to a theatre. The theatre is the biggest building needed in a worker block with 4x4. Minimize the loss of space by placing it at the far edge of a block - a 1x1 access to the road is enough for the patrolling worker to make their rounds.


Requirements: water, one type of food, attractiveness, washhouse, exorcist, theater, alcohol
Citzens: 25 per House, in total 950

Copper utensils are delivered the same way as alcohol.


Requirements: water, one type of food, attractiveness, washhouse, exorcist, theater, alcohol, utensils, medical herbs
Citzens: 30 per House, in total 1140

Build a herbalist at the block and a greenhouse somewhere in the city. I noticed that one greenhouse is enough to support two herbalists.


Requirements: water, two type sof food, attractiveness, washhouse, exorcist, theater, alcohol, utensils, herbs
Citzens: 35 per House, in total 1330

Provide a second type of food through the Shop, the combination does not matter.


Requirements: water, two types of food, attractiveness, washhouse, exorcist, theater, alcohol, utensils, herbs,news paper
Citzens: 40 per House, in total 1520.

Build news paper stand to unlock the final level of the worker houses.


And you should notice that there is one extra space for a worker building, increasing the number to 39, resulting in a maxed block to contain 1560 citizens.

Current shot of my city on Sandbox 4, with multiple blocks next to each other, only separated by 3x3 decorations.

Please note: this section is work in progress as I haven't yet figured out the most effective way to build blocks of manions. Later sections are based on my current best approach.


This left block has the downside that sometimes the last one or two buildings at then end lose their support of the buildings as the patrolling workeres turn around to quickly
The concept shown in the right screenshot has a circular layout similar to the worker block, but is not attractive enough in the middle the make the mansions expand to their maximum level.


The most efficient layout I found yet: Maintenance and Tax Collector at one end of the road, Emporium, Cafe and Spa at the other side. With proper roadblocks, it maximizes the range of the buildings.

Mansions are 4x4 in size, which means they are the quadruple size of a workers house. Aside from food they don't share any needs with the workers.
The only real reason to build mansions (aside from specified mission goals in the campaign) is that they provide inventors which are needed to build monuments.
Note that the buildings to support don't need human workers but 10 automatons each, which means two automaton factories can support a block of Mansions. They still need Maintenance and Tax Collectors. Notice that they have a lot higher range than the Cafe and Spa. The Emporium has the lowest range. Therefore the layout is: Maintenance and Tax Collector on the one side, mansions, then the Emporium and then Cafe and Spa. Don't forget to put roadblocks to maximize the range!
Actractiveness of the environment is even more important than to worker's houses. Keep industry away (the Emporium has some reach to the next storage building) and build as many and as large decorative objects as possible.

Requirements: none
Citzens: 8 per House, 120 in total
Basic Layout: Build Maintenance and Tax Collector at on end of the road, build 7 mansions on one side and 8 on the other. Surround everything with 3x3 decorations.


Requirements: three types of food, Cafe
Citzens: 12 per House, 180 in total

The Emporium has the shortest range of alle buildings, so build it close to the mansions. Build a cafe, which has a slighly higher range than the Emporium and let the patrolling automaton this their work.


Requirements: three types of food, Cafe, garments
Citzens: 16 per House, 240 in total

Garments are produced from silk and distributed by the Emporium, which has the same function as the Shop.


Requirements: Cafe, garments, Spa, three types of food
Citzens: 20 per House, 300 in total

Add a Spa to the block, which requires bottled steam to function. Also provide three types of food through the Emporium.


Requirements: Cafe, garments, Spa, three types of food, jewelry
Citzens: 24 per House, 360 in total

Jewelry is produced from gold and distributed by the Emporium.

• for a detailed guid on how to build production chains and how many citizens they can support see skirlasvouds excellent guide: https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=484205593
  
• To save workers: farms, monuments and steam extractors don't need to be visited by a maintenance building.
  
• Their is no distance limit for steam pipes, so build the steam condenser close to your mines
  
• if you run out of money, check if every worker house and mansion is visited by a tax collector and just wait and build nothing
  
• to minimize the negative impact on attractiveness of industrial buildings, build the houses and industry apart. Workers will communte any distance, even if the buildings are not connected via a road - there just has to be a road adjacent to the building. But goods can not be transfered that way...
  
• all buildings that produce a good will store a certain amount if their is no free space in a storage building or granary. But thos ressoures don't count towards "produce x amount of ressource in a year" mission goals.