Pasta is always a good cheap option, and it's dead easy to make a homemade sauce which is healthy and cheap. Can of tomatoes, some chopped basil, a couple cloves of garlic and a few spring onions are amazing, and you can add plenty of other things to it to make it more interesting. Or you can just sautee garlic in olive oil and use that as a light sauce that only takes 5 minutes to make. Crack an egg into it at the last second and mix it around with the pasta to get a creamy sauce.
I've also got a favorite cheap/easy recipe for rice and beans. Make the rice of your choice, or pasta works as well. Sautee onion and garlic, add sliced mushrooms and some dried basil, dump in a can of red kidney beans with some water (and flour or potato/corn starch to thicken it up) and simmer until it's got a good consistency (doesn't take long, just don't put too much water in). Don't add any salt: at the very end, add some soy sauce to taste. Amazing every time. It's what I cook for a visitor when I want to impress them. Also works great as a spicy dish, just toss in some fresh or dried chili pepper when you add the garlic.
Finally, noodles are always good. Not sure what's available where you live, but it's easy to buy packages with 5-8 bricks of instant Asian noodles here (not the crappy kind with the flavor packets in them). Wheat noodles have the best flavor. Briefly sautee some onion or spring onion, garlic, chili pepper, carrot, fresh ginger, mushroom, and Chinese cabbage in a pot, then fill it up with water and boil it for half an hour or so. Then toss in the noddles, give them 5 minutes to get soft, and eat. This works best if you have sesame seed oil for flavor, otherwise you'll want to add something else like soy sauce, chili sauce, or salt. Eat with chopsticks and drink the liquid out of the bowl at the end. Can also crack an egg into it at the end to make it more filling.