The Dart Monkey is an early game powerhouse that falls off in the late game. Its main draws are its good cost-to-DPS ratio for lower tiers and cheap Camo detection that lets the player save up for the mid game. In CHIMPS and Half Cash strategies, it's mostly used for its low tier upgrades; its higher tiers are niche. It benefits greatly from Monkey Knowledge, increasing its base pierce with Extra Dart Pops and providing one free use each game with Bonus Monkey!.
Spike-o-pult and Juggernaut should be placed at the end of long straight sections of the path so their projectiles travel over as much of the path as possible. If the map has places surrounded by obstacles, place these towers in those places.
Very Quick Shots is the best crosspath unless camo detection is needed. The third path's knockback buff to Juggernaut and Ultrajugg isn't worth losing the extra DPS from the faster attack speed.
Path 2
Triple Shot is a cost-effective early game option for a handful of maps like Dark Dungeons and Ravine.
Plasma Monkey Fan Club (PMFC) is good for CHIMPS late-game burst DPS but requires stalling or something to cover its downtime. Use Downdraft or Ice Monkeys to stall Ceramics at the end of rounds to give it more time to recharge.
Super Monkey Fan Club and PMFC pair well with Primary Mentoring, improving the fan club monkeys' pierce and range, reducing the ability's cooldown, and giving free tier 1 upgrades.
Fan club monkeys should be upgraded to Very Quick Shots. They can be upgraded on the top path too if extra pierce is needed. Do not upgrade them to Tier 3 or higher, as doing so prevents them from being transformed.
Path 3
Crossbow does decent early game damage but is held back by its slow projectile speed. Place it in areas where it's less likely to whiff.
Sharp Shooter is a decent stepping stone but needs pierce buffs to do well. Unfortunately, Berserker Brew makes it worse since the damage buff causes Ceramics to split into 16 Yellows instead of 4 Whites and 4 Blacks, further exacerbating Sharp Shooter's pierce problems.
Crossbow Master works decently in the mid-game, but falls off significantly past Round 80, as Super Ceramics take away its ability to layer-skip.
Like Ultrajugg, APM excels on maps with lots of closed-in blockers, making it extremely deadly against even tier 5 Elite Bosses if set up properly.
APM works best against Dreadbloon, which takes APM's extra Ceramic damage.
Outside of its optimal maps and Dreadbloon, APM is an option for Least Cash, Least Tiers, and Tier 2 of timed bosses. Otherwise, Glaive Dominus is generally better.
Optimization
Ultrajugg and APM work best on the following maps:
One Two Tree
Encrypted (place it inside the crypt)
Hedge
Moon Landing (place it somewhere can see inside one of the craters)
Sulfur Springs (place it on lower elevation)
Dark Path (place it where it can hit inside the walls)
Extra Dart Pops and providing one free use each game with 
Bonus Monkey!.