Cheapskater requires you to never buy an auto-promote.
This challenge is the ultimate 'Cheapskate' trophy attempt.
Although 'Cheapskate' trophy can be claimed even with having some amount of autopromotes bought (you just have to buy the least amount among other rankers), this challenge is strict zero-autos-bought run.
The only exception might be ladders with innate [FAUTO] ladder modifier.
Winning the round is very possible because this challenge is all-around normal playthrough, only problem might be promoting manually (might happen during AFK-time or you might get shot within 30-second manual promotion delay).