If you learn how to season oatmeal to your liking, it is a good, nutritious, cheap food. You can make loaves of bread out of oatmeal in a microwave. It's great once you learn how to do it, and a large loaf will last for many meals. Raisins, honey, brown sugar, cinnamon, nutmeg, ginger, pumpkin pie spice all go well together when making these sorts of breads. There are many other ways to season them as well.

Google is your friend. There are tons of recipes and ideas if you do some searches.

Quick breads are also cheap and easy to cook. You can buy (high-protein) bread flour in bulk from a food co-op. Bulk prices are often better.

If you can get an inexpensive rice cooker somewhere (or for Christmas), it makes rice cooking very easy. If you buy rice in large bags (20, 25, 50 pounds) you can often get a better price.

Watch for sales, and loss leaders, at your local stores.