Start with a Monkey Village
If your starting cash is $4,500 ($9,000 for bosses), then it's highly recommended you start by placing a Monkey Village first because you will save cash in the short and long-run. You can always sell it if you need emergency cash.

Permanent Discount on Self
Placing a Monkey Village next to a Monkey Village will discount them permanently, even after selling one of them. I also advise doing this as well prior to upgrading.

Why isn't my tower receiving bonuses like increased range even though it's clearly inside the edge of a MV?
So MV 1 has upgrades that were previously applied, you then upgraded MV 2 with Monkey Beacon to extend MV 1's range. Yet, when you place a tower inside MV 1's extended range right at the edge, bonuses aren't being applied. What gives?

Upgrading MV 2 with a Monkey Beacon will not extend the radius of a pre-existing MV in its current state. You need to change its state. To change its state, you need to perform an upgrade, or --if it's already fully upgraded-- sell and replace this MV 1 while it's in range of MV 2 with Monkey Beacon.

Base Price Discount
Placing a monkey within a MV will also discount its base price, not just upgrades.

Call-to-Arms Discount
Call-to-Arms, when active, will discount the base and upgrade price even further within its area of effect.

Monkey Town or Banana Farms first?
Monkey Towns first, then Banana Farms.

Why? Monkey Towns are most effective at earlier rounds the sooner you can get this out. This is because the income received late-game will gradually reduce despite popping so many bloons. The +50% income is meaningless if bloon value decreases over time. Eventually, you will be cash-starved. Once you have sufficient income, then go for Banana Farms and other cash-generating towers.

Will I get more bananas if I upgrade Banana Farms during a round?
No. Upgrading from 3 bananas to 13 bananas will not get you 13 bananas immediately*. It will take effect on the next round.
*However, if you place a Banana Farm for the first time, you'll receive 2 free bananas regardless of upgrades during and after a round ends. After that it will resume as normal; upgrades will take effect on the next round.

4/2 (Banana Research Facility) or 2/4 (Banana Investment Advisory)?
Always go for 4/2. See below.

Churning Out 13+ Banana Crates
At the end of a round, have a Banana Farm upgraded to 3/2 + enough cash to upgrade to 4/2 (Banana Research Facility). Start the next round then immediately upgrade to 4/2 (do not do this prior to starting the new round).

Why? Because when you begin the new round at 3/2, the game will think it is at 3/x (Banana Republic), which produces 13 bananas (plus 1-3 extra depending on Monkey Knowledge). If you upgrade it immediately after starting a new round, you will get 13-16 crates instead of 5-8 crates.

Below are several scenarios:
Assuming maxed out Monkey Knowledge and within a Monkey Village

Scenario 1 (no tricks): -$18,855 (upfront cost) + $5,328 (8 crates) [Round 1] + $5,328 (8 crates) [Round 2] = -$8,199 by round 2.

Scenario 2 (use trick once): -$18,855 (upfront cost) + $10,656 (16 crates) [Round 1] + $5,328 (8 crates) [Round 2] = -$2,871 by round 2.

Scenario 3 (Use trick twice, selling once in between rounds): -$18,855 (upfront cost) + $10,656 (16 crates) [Round 1] + $16,969 (sell) - $18,855 (upfront cost) + $10,656 (16 crates) [Round 2] = $571 by round 2.

If you're lazy and flush with cash, you can stick with scenario 2. If you're greedy, then scenario 3.

Banana Investments Advisory - Should I withdraw early?
As your investment advisor, I would not. Besides compounding interest, you will get a giant payout at the end of each round, and not just during the round. I suggest not emptying it too early when it stops at $19,xxx during a round because it will jump to $20k at the end. If you empty it early, you will not be given any payout. Then again, I don't recommend this upgrade path. Stick with Banana Research Facility.

I want my Bananas now!
Jungle Drum, Call-to-Arms, Overclock, and other speed boosters will accelerate Banana Farms.

Game Suggests To Put Them at the End of the Track. Makes Sense!
Not recommended unless this end track runs parallel to the starting track (see MOAB-SHREDR below). It's either inefficient use of resources just to catch a few stragglers (the older spikes will disappear after a while), or there's too many stragglers that got past your frontlines because of poor strategy (you'll end up panicking and making poor decisions like throwing down a ton of road spikes), and they won't be saving you.

If you must use them early the first few rounds to catch a few stragglers, because of a Monkey Teams event, then leave it at 0/0 or 1/0 (you'll sell it later anyways). Always place it within a Monkey Village and prior to a fork. If MV is restricted, then place it outside the range of your frontline troops. Remember, your frontline troops should do the heavy-lifting, and not this lonely Spike Factory hiding in some corner in the distance.

MOAB-SHREDR - MOABs Only!
When upgraded with MOAB-SHREDR Spikes, place them near a track on the opposite side in such a way where a MOAB will be wide enough to touch those spikes, but not the bloons themselves. Spike Factories can also be placed in areas where it's not close to any tracks such as when it's above a tunnel, to ensure only MOABs touches them. This is only practical on some maps.

For maps that are impractical, place them way out in front within a Monkey Village for maximum effectiveness. Huh? Wouldn’t the Bloons just clear the path? That’s true only if it’s not supported by other towers such as Ice Monkeys, Glue Gunners, and other Bloon-killing towers. Allow Spike Factories to soften MOABs up before other towers because if you allow other towers to rip open a ZOMG or BFB before Spike Factories can work their magic, ZOMG's children will come spilling out and all that Anti-MOAB damage that could’ve been inflicted on MOABs is now wasted on its children. Every time a Spike Factory throws out a spike, it will hit the fat MOAB before it hits a bloon. Also see Spike Factory + Bloonchipper Combo in next section.

Scatter or Yeet
When placed in an area not close to a track, it will disperse spikes randomly around it. The reason you'd want this is so it hits MOABs only, usually above a tunnel. If you use Spike Storm ability, it will find a random spot on a track and yeet those spikes across the map to that one spot on the track. It will find another random location if you fire Spike Storm again.

When a Bloonchipper sucks in a MOAB, it will eject it out in the rear. Place Spike Factories with MOAB-SHREDR behind it so that those MOABs gets ejected into them for a brief second.

Absolute Zero on Bosses and MOABs
Absolute Zero will slow down bosses and MOAB-classes permanently.

Ice Shard Chain-Reaction - Anti-ZOMG-Rush
Ice Shards will do massive damage if you can break open the first ZOMG and release its bloons, triggering a chain reaction when the shards breaks open nearby ZOMGs and other MOABs. I like to place a Glue Gunner in front of the Ice Monkey and/or an Ice Monkey w/ Arctic Wind upgrade to slow down the bloons and concentrate ice shards. You can use Engineer's overclock ability or Monkey Village's Call to Arms ability to increase rate of fire. This tower can potentially become the most powerful than even the Temple of the Monkey God at a cheaper cost. Be warned however, when using Ice Shards in Contested Territory especially on higher rounds because it can "freeze" the game if running on potato hardware.

Artillery Barrage Stuns and Pops
Artillery Battery ability can pop bloons a few times besides stunning. The game description doesn't say it.

Super Monkey Fan Club
In addition to the rapid-fire darts, they will still fire their primary weapon such as triple darts or giant spiked balls.

Bloontonium Overdose
Bloontonium Reactors will stack cooldown reductions. They will not stack on popping bloons unfortunately.

Ray of Doom - Cross Those Streams!
One Dartling gunner at 4/2 is weak against MOAB-classes at first, but when combined with multiple 4/2 Dartling Gunners, they become very powerful. 12 Ray of Dooms > 12 Area Denial System. In fact, the beam grows wider and stronger (you can't see it). Even if you don't aim directly at MOABs, the intense heat it gives off will pop them.

Bloon Trap
This is obvious, but if you upgrade to Bloon Trap, I suggest not upgrading “Larger Service Area” because the bigger radius will sometimes throw the Bloon Trap on a path where you don’t want it, thus depriving you of extra funds.

Overlapping Towers
Place the Chinook furthest away from a tower you want to redeploy. Redeploy that tower. While the Chinook is on its way to pick up the tower, you can do the following:
1. Quickly place another tower at the location where you’re redeploying.
2. Quickly redeploy another tower with a different Chinook.

If you do it quickly enough before the first Chinook places the tower in its new location, you’ll have two or more overlapping towers.

Redeploy Temple of the Monkey God
Did you know you can move TotMG? This method only works prior to sacrificing your towers.
Place the Chinook far away from the 3/x Super Monkey. Redeploy the Super Monkey where you want to have your TotMG at. While it is on its way to pick up the Super Monkey, QUICKLY upgrade to TotMG. If you don’t do it quick enough (Chinook picks up Super Monkey BEFORE you hit “Proceed”), the game will CRASH. This is because the Super Monkey has temporarily disappeared while it’s in transit, and it doesn’t know where it is.

This is useful for clustering a bunch of TotMG together without sacrificing TotMG nearby.

In Monkey Knowledge, there is a book called “Activated Ability.” Read it if you haven’t done so.

So every time you activate an ability, you get those extra bonuses.

Infinite Activated Abilities
1. Upgrade your Engineer to Overclock or your Heli Pilot to Chinook Support.
2. Press the Overclock or Chinook Redeploy ability, but do not click on any towers. Just click the ability again to cancel out of it.
3. Simply by clicking on the ability icon, you’ve just activated “Activated Ability” bonuses. Just keep pressing the ability and watch your cash and HP increase, bloons getting stunned, etc.

Want to know what's the most economical sacrifices to offer to the Monkey Gods? Read on!

Note: this guide assumes you've acquired maximum discounts from Monkey Knowledge.

There are guides out there for TotMG so here's several links:
https://bloons.fandom.com/wiki/Temple_of_the_Monkey_God
https://bloons.fandom.com/wiki/Temple_of_the_Monkey_God/Sacrifices

The goal is to sacrifice just enough towers to reach $30K in the most economical way possible. It is capped at $30K so spending any more than this is considered waste. We are trying to reduce that waste as much as possible.

Notes:

• [Y] and [N] means place inside Monkey Village for discount: [Y]es or [N]o?
  
• Add up the towers and multiply by 1.3 (30% sacrificial savings if you got the Monkey Knowledge). This will be your "Total."
  
• A "*" next to the tower name means recommended sacrifice. Some towers are worth sacrificing despite it having higher waste because they can be useless late-game.

Mortar*
4/4 [N]: $11,945
4/0 [N]: $11,260
Total: $30,167

Bomb Shooters
4/1 [N]: $5,940
4/0 [N]: $5,750
4/0 [N]: $5,750
2/4 [N]: $5,655
Total: $30,024

Ice Monkey*
4/0 [N]: $12,950
4/0 [Y]: $10,975
Total: $31,103

Glue Gunner*
4/0 [Y]: $12,195
4/0 [Y]: $12,195
Total: $31,707

Monkey Apprentice*
4/0 [N]: $11,675
2/4 [N]: $11,480
Total: $30,102

Dart Monkey*
0/4 [N]: $7,820
0/4 [N]: $7,820
0/4 [N]: $7,820
Total: $30,498

Boomerang Thrower
4/0 [N]: $8,535
4/0 [N]: $8,535
4/0 [N]: $8,535
Total: $33,287

There are many other towers you can sacrifice, however, I do not recommend sacrificing them because they are more useful than the above abundant towers.

Place a lot of 1/2 Ice Monkeys and 1/3 Glue Gunners (we don't want to hurt the bloons). Then build 0/4 Snipers and x/4 Helis. The Ice Monkeys and Glue Gunners will slow the bloons to a crawl without popping them, giving you extra time to use Chinook crates and Supply Drops many times. I suggest putting the cash monkeys near a Monkey Village upgraded with Energy Beacon to reduce cooldown.

Monkey Intelligence Bureau + 1/3 or 1/4 Spike Factory will not do much damage against it so don't bother. You need to upgrade Spike Factories with White Hot Spikes.

Monkey Teams events does apply in boss events.

Always spend them on Firework events, and nothing else. Generally I avoid Halloween and Christmas Fireworks events because of useless aesthetics. I'm from the USA, so we get July 4 Firework events. The payout is worth it. If you also get the bloonstone festival event, then it's a cherry-on-top.

What you get:
City Cash, Bloonstones, Monkey Knowledge, Supply Crates, Bonus Monkey, Red Hot Spikes, Monkey Boost, Boss Powers, and other exclusive aesthetics.

If you progress normally (level 40 and all towers researched), don't miss a boss fight, play Contested Territory from time-to-time, and spend all your bloonstones on Firework events; then we're talking about 2.5 - 3 years of grind. Knowledge Packs will take the longest, and you will dread it.

Speaking of Knowledge Packs, you'll get wildcards that you can use on any book. Avoid the temptation of dumping it all on one tower as you approach closer to level 15 because all you'll get is cash. That's wasted XP. I use wildcards as a "No-Tower-Left-Behind" crutch.

I honestly don't care about achievements, but if you must know, I never got DDTs and lead bloon because they don't occur often late-game :(

If you hate money, sure. You will earn more by being a war-monger than a pacifist, even if you never defend and lose.

Yes! But you'll need multiple devices with BMC installed to accomplish this. If your profile is on 4 devices, all synced so you see the same opponent(s) across all devices, you can launch four attacks against them. You can even "go back in time" and launch the attack again by using an older out-of-sync device, backing that up to the cloud, and loading it to the up-to-date device (you'll lose progress so be sure you don't progress too much). In theory, you can install BMCs on VMs (Virtual Machines), but I haven't tested it.

This is great for farming MvM assuming the player retaliates multiple times.

Because this game is free, there will be micro-transactions. If you want to support the developers, I recommend purchasing 3 Banana Farmers over everything else (3 banana farms per farmer).

Spotters
For maps with restricted Banana Farms, Monkey Farmers can act as spotters for Monkey Subs, which is why I highly recommend buying 3 Farmers especially when a Monkey Teams event requires only Monkey Subs and a couple others.