I was on a tight budget through grad school and my first job outside of it:
Mac and Cheese
Hot dogs
Scrambled eggs
Any type of soup
Pasta and sauce (toss some veggies right in there, like peas, zucchini, etc.)
Naomi. . . I mean, Hamburger Helper. Get it? It was her costume!
Honestly, buy fresh fruit and vegetables, and prep it yourself. Apples, oranges, bananas, broccoli, it's all reasonably priced.
Alot of times, as well, you can make things yourself and "batch cook." Instead of making a can of soup, buy the ingredients and make three or four meals out of it. Some soups freeze really well. You pay up front with groceries, but save money through the week, and it may seem like it's adding up, but you're saving in the long haul. Buy a big bag of chicken breast cutlets, and make several at a time, cooking and adding whatever sauces you like. . . there are cheap ways to make several! The food is prepared and all you have to do is toss it in the microwave. . . you'll be less tempted to go out and grab something if you need to eat quickly, and it's already in the container for travel. This is better for you, too, since if you've ever seen sodium content in packaged foods, it's incredibly high!
My friends go to the store on Sunday, and they cook everything they're going to eat through Friday that afternoon. . .
There are some VERY easy things for you to make, so you don't need to really know how to cook. . .