My advice would be to get a part-time job at a smaller independent restaurant - do anything they want and ask for leftover food at the end of your shift. If you work hard and are polite you can get a lot of your food needs there plus add $$ to your $80 budget.

They may even show you how to cook if you ask nicely.

Homeless people are also good at budget eating. You may want to spend 72hrs on the street with one and learn some skills.