Ramen noodles are cheaper than mac&cheese now unless the mac&cheese is on sale... but ramen (mr noodles) are really gourmet with just a bit of onion and some veggies, and maybe a bit of meat. The oriental or vegetable flavour ones are the best for that.

Making soups and stews with a slow cooker is really helpful.

Look up the books by Euell Gibbons, you can pick some foods from what are often thought of as weeds, that are often more nutritious than common vegetables found in stores.