Have you tried Easy Mac? Kraft makes the original, but there are several store brands as well. It's really good, better than the boxed kind you boil on the stove.
You can start with 2-3 packets of Easy Mac and turn it into all sorts of casseroles.
Add a small can of tuna, small can peas, and a can of cream of mushroom soup (opt) for tuna casserole. Heat in the nuke, topped with grated cheese.
Cook 1/2 lb. ground beef with a little chopped onion (onion flakes are OK),
drain and season with salt, garlic/herb seasoning & pepper. Cook the pasta, combine with meat, a small and of corn or mixed vegetables, and a small can of tomato sauce or drained chopped tomatoes. Heat in the nuke, topped with grated cheese.
Or substitute a can of chili beans for the vegies, in the above recipe, and substitute chili powder or Southwest seasoning for the garlic/herb seasoning. Add additional hot sauce if you like. Top with grated Mexican style cheese.
Steam a chicken breast in your nuke, and chop while the pasta is cooking. Combine pasta and chopped chicken with a small can of peas and carrots, cream of chicken soup, and top with crushed Ritz crackers.
Get some thick sliced (1/2") good ham from the deli, chop, and add to pasta along with box of frozen broccoli florets and a can of cream something soup. Top with crushed Ritzcrackers or cheese.
By the way, use the sauce packet that comes with the pasta for all the above.
All of the above recipes work just as well with quick cooking rice.
Rice-a-Roni and Zatarains make some great mixes, and you can improvise with these just as easily as you can with the Easy Mac.
You can make soup, meatloaf, chili, spaghetti sauce, baked beans with smoked sausage...your imagination is the limit.
Necessity is the mother of invention.