All dried food, noodles, pasta, rice, crackers, nuts, beans, pluses. These all need dehydrating, most just by boiling in a pan of water. Beans need soaking over night. Things like pesto sauce will add flavor. But even cheaper are canned tomatoes they make an excellent sauce. Always help yourself to extra salt & pepper, sugar & sauce sachets from cafes, dinners, restaurants. You can add these (not too many) to the tomatoes for a tasty sauce. If you can afford a few dry spices....mix into tomatoes over the heat...oregano gives an itallian flavour. cumin gives an indian flavour. curry powder even more so. Try adding vegetable stock cubes to make a noodle soup. Get store brand canned veg & dry fruit. When you have money to shop because they'll keep for ages. Oh & invest in tupperware to keep packets in to avoid pests pinching your supplies.
Trail mix and dry cereal.
Geez, that would leave Peanuts, Apples, and Beef Jerky. Oh, wait, cheap?<br />
Pop tarts :D