A bit cheaty but the idea is to get a map where the 2 starting lanes run in parallel for a bit so you can place towers inbetween.

1 Main lane is kept short and closed last.
The other main lane is developed so that when it branches of, you try to develop the tributaries in a way which space out the mobs, while choosing to develop the tributary which has a chance to loop back around the citadel.


In the screenshot you see:

• m1 - Main Lane 1 was not developed until the very end. A short lane spawns not as tough waves.
  
• m2 - Main Lane 2 branches off to the side and then into 2 tributaries.
  
• t1 - Tributary 1 spawns mobs too close to the main defence so that they arrive there together with Main Lane 1 mobs. I tried to develop it further but got unlucky as it branched off again.
  
• t3 - Tributary 3 was very lucky as it spirals around the citadel allowing for later placement of Obelisks which can work the Tributary 3 lane but have a Progression priority so that they can get some shots on Main Lanes 1 and 2 if it gets too dicey.

I kept developing Tributary 3 the longest and put some towers around there so that they can put some pressure off the arriving lanes. They ended up working too good and well enough even for Big Brain.

After looking up the enemies in an online wiki as the ingame monster manual isn't listing all, the following are the most dangerous:

First Enemies Ceiling: 800HP, 1500 Armor (ram)

• Before the first boss Ballistas are okay for most starters but struggle with armor and too much mobs
  
• The first Obelisk will focus on armor, a bit of HP, while you need to get Mana income going
  
• You likely won't reach 1250 armor damage on this one before shifting to shields but might want to develop that later before the missile guys come in
  
• Keep building Obelisks with 20x Health and 20x Shield Multiplier. Keep targeting at "Progression", space them out well so they don't target the same enemies, make them cover the 2 main lanes at once, even if it's just the tiny bit around the Citadel so they can last-minute snipe some guys
  
• On my screenshot the last 3 out of 12 Obelisks don't cover both lanes anymore but focus on the ones which are developed furthest

Second Enemies Ceiling: 5k HP, 2k Armor, 4k Shield

• After the first boss shields are introduced with 4000 Shield enemies.
  
• Get one new Obelisk up and running levelling shields

Demons: 7k HP, 12k Armor, 2k Shield

• Here you want your first Obelisk to reach 1250 armor to snipe missiles (most armor targetting)

Brains: 10k Health, 9k Armor, 12k Shield

• Very Shield Heavy with the Super Fast Eyes which spawn from enemies (1k Health 2k Shield, -5 base damage from all attacks)
  
• First I over committed on those eyes trying to get the Obelisks to 1-shot them, however that means those Obelisks are not good for the rest of the spam
  
• 20x HP damage and 20x Shield damage seems to be within a sweet spot good enough to deal with the waves

Big Brain Oogie:

• You need to switch targeting from Progression to Slowest for Obelisks in range so that they don't get distracted by the many spawns of the final boss and actually finish it before it gets too far up your defence and is allowed to last minute vomit kill you

• Obelisk Upgrades, especially Shield Damage to get to +Range early. Careful though as it is possible that after Range you need to invest heavily into Mana as shooting at additional lanes might enable towers which before did not work that lane, leading to them emptying your Mana pool on another lane and leaving you with no Mana when another tributary arrives at your citadel.
  
• Poison slowing down enemies is huge, seems good for bosses especially
  
• All Obelisk Upgrades except for Monster Studies
  
• Mana Siphon, Mana Bank, some Mana Upgrades for +% of your total pool and increasing the total pool
  
• Crit, Quality over Quantity fits the style though I didn't do the math
  
• Poison, potentially Bleed/Fire/Poison effects if nothing comes up
  
• No need for Banditry, Mines, Haunted Houses, Ballista upgrades