BUY SOME VEGETABLES.
I lived on various forms of minestrone, lentil soups and frittata for a few years while a student.
They;re easy to make.
General principles are to put some onion, celery, carrot and garlic cut up in a pot with some oil, and let them slowly cook but not brown. Then you can add water, salt and pepper and the vegetables you find in season - spinach is always around, swiss chard, pieces of squash, zucchine, escarole, peas, potatoes etc, and cook around an hour, so everything is softened and the soup is not just water and vegetables floating in it, but has some color. Drain a can of chick peas or beans and let it cook another five minutes or so. Some people like stuff from the cabbage family like broccoli or cauliflower or cabbage, and it can make a great soup, but it will dominate in the taste. You just have to spend a little time frying the first stuff and the rest does itself. But if you only have garlic, or onion, or onion and celery, go with that. At the end, throw in some pasta (small pasta is best, and it can be a mixture of different kinds) and cook till done, or cook it separately and add (throw in leftover pasta too).
For lentils, fry some garlic, smashed, in the oil, then add dried lentils and water. Let them cook. depending on the lentils they may take an hour or so. They should get soft. You can also add celery and carrot and during the cooking add a package of frozen chopped spinach (this is not a gourmet recipe, but for a student not to starve) (you can also add fresh spinach of course, but you can keep the frozen on hand and it's cheaper). Cook some rice and mix in or some pasta, or toast some hard bread, rub with a piece of garlic, put in the bottom of the bowl and pour the soup over it.
Beans, chick peas, lentils, mixed with grains (rice, pasta, bread) equals a whole protein like steak. The lentil soup will supply iron.
This is cheap cooking, and easy, and you can make it for a couple of days. It's also very good.
For frittata, put oil in a frying pan, slice up an onion (minimum) plus vegetable (sliced zuccine are standard, but peppers, or potatoes, or other things you like, alone or in combination are fine) with salt and pepper and cook over low heat till cooked. Mix eggs with a fork, add salt and pepper and pour into the frying pan. Cook, covered, on low heat. When it's almost set, slide it out of the pan onto the cover, and reverse the cover over the pan and cook the other side till it gets a little lightly browned.
Pasta is great with vegetables, esp if you;re sick of tomatoes.
Slowly cook some cubed or grated zucchini or cut up cauliflower in oil with garlic and/or onion until its very soft. MIx in with the cooked pasta.
Or take a can of tuna and some garlic. Fry the garlic slowly in oil, when it's soft, add the tuna, fry for a few minutes and put directly on the pasta.
In the end, buy vegetables. Buy vegetables. Buy vegetables. The beans and chick peas and lentils and the starch will fill you up and provide all the protein you need.