I try to eat fairly cheaply and I've read some basic ideas of those who do live very cheaply. Some of the things they cite eating are oatmeal, rice (and other grains) and beans/legumes. I tend to eat a lot of those things naturally because of my chosen diet. I also bought a book called "More with less" and someone here recommended it. You might want to see if your library happens to have it. It talks a lot about how to eat fairly healthy but doing it cheaply.
I know other people here have mentioned hillbilly housewife
and I've mentioned before my favorite blog of a woman who feeds her family (her and her two sons) on $3.33/day. She doesn't always include recipes but it is good to see what type of stuff she is eating: