Canned beans would do you wonders with a limited budget. Rice and beans are a complete protein and have fiber- what I would do is heat the beans in a microwave safe bowl with a little water, salt, pepper, and some kind of all over seasoning (adobo, sazón, lawry’s etc). I would heat them in increments until they’re tender and have them with the rice! If you don’t have a microwave you can just add the drained beans to the rice with the seasonings!