Rice and beans.... and while it might sound bland, it can be DELICIOUS if made right!
To do it on the TIGHTEST budget, buy them both in bulk.... dried beans and regular cooking brown rice. Soak the beans ahead of time (they can be frozen after being soaked and cooked). Use stock to cook the rice (homemade chicken stock or veggie stock is the healthiest and cheapest), add things like cilantro, parsley, etc.....whatever you can get cheapest or have on hand and whatever you prefer. Add a side of a green veggie and you have a healthy balanced meal.
Also fried rice can be done easily and cheaply and delicious at home. Make a big batch of brown rice and set it aside. The "traditional" way of making fried rice includes chopped meat, a scrambled egg, and peas and carrots. I throw in whatever leftover meat I have on hand (if I have a small amount of meat left from a meal, I will often chop it and put it in the freezer SPECIFICALLY for fried rice in the future). I also use fresh steamed carrots (bought in bulk is one of the cheapest veggies out there) and will only throw in peas if I happen to have some in the freezer. I've also thrown in onion, broccoli, bok choy, cabbage, green beans and bean sprouts. The egg is another "optional" item in my book. If I don't have any meat, I will add the egg, but if I have enough meat, then I don't worry about it. Anyhow.... stir-fry the veggies and scramble the egg, throw in the meat to heat it through and then toss in the rice... stir over medium heat.... I try to get a few crusty bits of rice going.... yum! And then toss together with some soy sauce and a bit of worcestershire if desired. Reheats well for lunch the next day. But I will say that it doesn't freeze particularly well... the rice gets a bit mushy when reheated.
Split pea soup is another really filling meal. I can make a double batch with about 15-20 minutes of hands on time and probably under $5. Four cups of of split peas, 1 bay leaf, 1 C chopped onion, 1 C chopped celery, 1 C chopped carrots, 4 quarts of water, salt and pepper, and a ham bone. Now, IMHO, the ham bone is totally optional, but it does add a very nice flavor. If you don't have a ham bone but want the taste, ask at the market or butcher shop. They may offer you one for free. If not, buy a small piece of canadian bacon or even salt pork to use for flavor (although the salt pork will add a lot more fat). Anyhow, I can provide directions if you are interested, but this is SUPER filling, healthy, delicious and CHEAP!
You can also play the "pantry" game and figure out meals from whatever is lingering in there! Not every meal needs to be a totally balanced Good Housekeeping-worthy event! Pasta and canned tomatoes... DONE! Vegetable soup made with a bunch of drained and rinsed canned veggies plus a few crackers or toast... GOOD ENOUGH!
Desperate times call for desperate measures. I hope you are able to create some healthy, filling cheap meals and still save the money that you need. Good luck.............P