A rotisserie chicken from the grocery store is $5. You can eat it hot, then make chicken salad, then boil the bones to make soup on the last day.
Quesadillas are also incredibly cheap and friendly. Buy some tortilla shells and shredded cheese, and throw whatever random ingredients you want in there. A can of beans is like 80 cents. If you bake it instead of microwaving it’s actually pretty good.
The best and cheapest food of all is homemade soup or chili. Basic chicken soup (starting with your bones above) is basically just that plus carrots, celery, onion, and some kind of starch. A bag of baby carrots is like $1.50.
Chili is also incredibly friendly. Basically just saute an onion and add meat, spices, and vegetables of your choice. A lot of the ingredients in chili come from a can, like beans, corn, tomato sauce, etc. You can make a huge batch that will last for days.
Another secret to having lots of cheap food- make a big batch and freeze the extras in individual tupperwares. (I always buy the same kind/ size of tupperware so they all match.) Freeze some of the leftovers on the same night when you make it, and then heat up the rest on nights when you don’t feel like cooking. Soup, casserole, spaghetti, curry, and many other foods freeze really well.
Also, try to keep on hand cheap foods that have a long shelf life. I always have canned veggies, sauces, spices, carrots, potatoes, and onions around. Shredded cheese freezes really well also; you can buy it on sale and use it to make lasagna, mac and cheese, quesadillas, etc. For breakfast, look for cheap healthy things like oatmeal, apples, peanut butter, etc.
Eggs are also incredibly cheap and filling. You can make a quiche out of eggs, cheese, and any random veggies you have around. Or make your own Chinese fried rice with eggs, peas, carrots, rice, and soy sauce. Just take the cooked rice and sizzle it on the pan with oil and soy sauce, then stir everything else in. (One of my friends lived in Hawaii for a while and makes a tasty version with spam; $2.50).
Making your own baked goods from a mix is also really cheap. A box of muffin mix is like $3. That’s about the same price as one single pastry at Starbucks. Basically cooking for yourself is so much cheaper than buying convenience food, and not that much harder. With a few basic recipes and proper food storage, you can make that money last ten days and then some.