One of my favorite super-cheap, super-flexible meals is stir fry. As a lover of all things salty, soy sauce in particular, stir frys are always a staple. You can use virtually any kind of rice, veggies, and/or meats.
This is what I had left in my freezer/cabinets:
1 bag frozen mixed vegetables
1 cup white rice
1 cooked steak (not sure what cut)
1 pint mushrooms
1/2 bag frozen edamame
While the edamame and rice were boiling (follow directions on box or bag) I put the veggies and mushrooms into a frying pan with about 4 tbsp. soy sauce.
I cut the steak into small chunks, and added that to the pan. Once the rice and edamame were done, I put all the ingredients in together with some more soy sauce and a healthy sprinkle of garlic salt.