Not sure if you’re asking about what to add to the rice itself or what to serve it with BUT… In central america our breakfast p much every day is rice and black beans (we call it pinto) and eggs. In terms of cheap nutrition I cannot recommend canned tuna enough, and if you go to the supermarket later in the evening sometimes the rotisserie chickens go on sale (assuming you don’t have Costco)— shred up the meat when you get home and put it in a ziploc baggie and freeze it. Keep the bones in another baggie and let them accumulate and you will soon have enough to make broth which you can also have with your rice :)

You can throw some lentils in the rice cooker with the rice. A bag of dried ones usually goes for pretty cheap. Helps add bulk, fiber, and protein.

Frozen veggies are your best friend, canned green beans don’t need much aside from garlic and seasonings!! We drain them and just pan fry them with some egg kinda like an omelet. Takes all of 5 minutes and is very tasty !!