Bloons TD 6 Guide

Usually I begin with 2 Boomerang Monkeys and get them both to 2-0-2 or Glaives and Red Hot Rangs which will hold back early game bloons relatively easily until round 24 when camo bloons are introduced.
Subsequently I place down my camo support tower of choice, in my case the tower is Etienne or, if you do not own Etienne, a village will also work but cost you slightly more, each camo support tower mentioned above have their own setbacks, (Etienne has to reach level 8 before the UAV provides camo detection and the village has a limited range but you can get camo detection instantly although for a price)
Once I have my camo detection tower set, I generally drop 2 more boomerang monkeys and upgrade one of them to 3-0-2 or Glaive Ricochet plus Red Hot Rangs and upgrade the other boomerang monkey to 0-2-4 or Faster Rangs plus Moab Press.
That will easily let you beat the MOAB when it arrives.