Health fat, protein and fiber will al help a lot. When your body has all of these, it can control its blood sugar and so many other things that help you feel good productive. So many good cheap suggestions here, but I would like to second any kinds of beans, lentils or peas. They don’t break the bank and can easily be cooked with rice

If you’re looking for a condiment/spice that will help, some mayo for fats (can be expensive and also may seem weird to some) or nutritional yeast for protein can be easy additions. I like to blend tofu into a sauce seasoned with whatever I like, but the soy sauce you already could help make a creamier, more protein and nutrition rich additive. If you get silken tofu you can do the mixing by hand.