I'm pretty poor, and I go to a college out of state, so I've noticed that the area you live in really has a significant influence on your diet. In my college's town, there's a very cheap grocery store, and I get a lot of canned foods and cheap carbs(rice, pasta, etc) from there. Then there's a local farmer's market that's actually incredibly affordable, so I got very lucky with that.

However, in my hometown with my parents, everything's really expensive. I found the healthiest foods that'll actually fill you up and are basic, affordable staples to a diet are cheap non-brand name cereals(Cheerios-like products, they last a while, look for the bag cereals, they're usually cheaper, and they're whole-grain, so they're actually healthy compared to sugary counterparts), apples(usually pretty cheap compared to most fruits, I don't like them much, but that's just a matter of taste), clementines($5 a box, typically...oh so tasty, works as a dessert, too; keep them in the fridge and they last longer), rice, pasta, and general sandwich stuffs. Also, canned soup is cheap and tasty, and usually gives you enough nutrition to last you the day. Good for winter.:3

I usually just eat what I want whenever I want, but I'm definitely not unhealthy. My parents don't really keep anything healthy in the house to snack on, so I really have to dig around. If you look around enough, you'll probably find something healthy. Or else, maybe drink water a lot?^_^;;;