I have been making this really great bean salad this summer. Two cans of beans, a can of corn (fresh corn might actually be cheaper right now!) chopped red onion, chopped tomato, some vinegar and oil, salt and pepper, any spices you might like. Some cheese and sour cream if you want. Some avocado. You can serve it as is, on rice, on salad, on a bagel with cream cheese, with chips. Use any combination of these ingredients, and anything else you can think of. Oh man it's great!

also: once a month or so I put together a big batch of museli. It's like granola without adding sugar or baking it. Raw oats, whatever dried fruit and nuts you want (sunflower seeds and raisins are pretty affordable). I have it with milk every morning with a hardboiled egg or two.

I also enjoy BLTs and sausage sandwiches quite a bit. Canned sardines are also amazing. They are very cheap and you can throw em on a salad.

Some foods, like the avocado, nuts or meat seem expensive when you're at the store but you seriously need protein and calories and fat and they are completely worth it. There is basically no point in even eating if you are not getting protein and calories and fat. The secret is to get as many versatile items as you can. Try not to get a lot of items that can only be used for one specific kind of meal. Then you can mix and match all week!