When I was crashpadding in Bayonne, I broke my staples down into CapnJim's Basic Food Constituents: Protiens, Carbohydrates, and... Green Stuff.
Protiens: Chicken is cheap. So is ham, canned tuna, eggs and beans. Milk. Gotta have milk.
Carbs: Dosen't get any cheaper than rice. And rice goes dern good with chicken and beans. But have some pasta, pototoes, flour and wunna' bred on hand too, cause rice is about as boring as it gets.
Green Stuff: I like raw spinach, good dolla-to-nutrient ratio, and it tastes good. But it goes bad if you don't eat it. So, cans it is. Canned corn, peas, collard greens, whatever. Just get some veggies in there. Limes, lemons and some OJ are good too. Keeps ya from gettin' scurvy. Survy! I love that story.
After that, you just have to have some fillers. Honey's good. Cheap and packed with energy. Peanut butter is the same way. Salt and peppa, mustard, mayo, ketchup. An onion. Budda or olove oil. That kinda stuff.
Then you just have to pick one from each category, throw it all together in some creative way that won't make you gag, and bob's your uncle. Cheap eats. Chicken, rice, and beans. Sauteed anion and ham pieces in pasta with a cream sauce made from the flour and milk. Mashed taters. Egg salad. So on and so on. Ad naueam.