I was over 3m coins at one stage, now I need to use spare stamina on chop chop to keep myself from going bankrupt.

Originally Posted by Largepotato

I was over 3m coins at one stage, now I need to use spare stamina on chop chop to keep myself from going bankrupt.

Try doing the later event stages instead. They have quite a good return on gold, plus you get other drops.
The second best would be 12-5, while skipping the optional secret garden if you're focused on gold.

If all you care about is gold, then the gold mission (ideally while running gold boost as well) is definitely the way to go; during the boost time I usually end up earning about 1.5M gold on average (burning about 5-6 FGs as well) with the slowest squad clocking in at 561 speed.

Otherwise, I second Volarmis' suggestion about running 80 stam event stages (particularly in phase 2).