i start at wave 16 with jester and tower boost, i upgrade all the buff beams then the app/squire towers right after since this wave is short.
wave 17 i switch to upper summoner (genie-airplane) to upgrade all the auras + overlord heal everything.
i also place my 3 guardian summoners (2range 2dmg 2speed guardians) behind the towers so the belt doesnt move them.
the buffbeam, app/squire towers have to be placed as close as possible to the wall behind them.
i usually restart after wave 20 because the loot multiplier gets significantly worse after 19
here are some screen shots to help you understand the build: https://imgur.com/gallery/hZgVbHR
note that it isn't an easy map and most choke points are uncomfortably close to the cores so proper placement is key