I would go for a Hobbywing Justock ESC/17.5 combo.
Simple.
Cheap.
Probably fast enough to not be the problem if you are not keeping up on track. Meaning, if the speed difference between this setup and whatever the "best" setup is (that will cost 2-3 times as much) is enough that you are not competitive, then you are a very good driver racing with other very good drivers.