Big bag of lentils. Big block of low-cost cheese. Canned and frozen foods are convenient, but expensive compared to fresh. Use salt, pepper, and other seasonings/herbs/spices to enhance flavor (where I shop, name brand jarred seasonings/herbs/spices are expensive, but many common seasonings/herbs/spices are available and less expensive in plastic packages in the ethnic foods aisle. Buy veggies and fruit carefully, and only what is in-season locally (prices will be comparatively low).
No sodas, no coffee or tea, just tap water.
Check to see if a nearby church has a food bank
Walk when possible.
No entertainment except what is free at the public library (a good library will have a lot!).