One cheap food is canned chicken noodle soup, and put a can of mixed vegitables in when it is heating. Both foods can be kept on shelf for long time, and only one pan to clean up (if one eats the soup out of the pan)
Another good one is frozen burritoes. you can usually get 20 packs for about $5. if you can afford sour creme, that is good to have also.
Lastly, pasta. this is a mainstay, espcially easy if you are off campus. (in a dorm it makes a lot of steam, to it may be better for after graduation.) however, it is by far the cheapest food that one can eat lots of. (also hot dogs, for protein.) one can pour a bit of sauce on the pasta directly from the fridge, and the spagetti has enough heat so heating the sause separately is not necessaary (and saves dishes).
staying with the off campus mode, it is fairly cheap to get a lot of hamburger, shape the hamburgers with syran wrap (i know it is misspelled), and freeze them. they can last about 3 weeks in the freezer, and needs only one day to defrost. (also good for an occasional protein fix.)