I am gluten intolerant and various other food sensitivites.
Here’s my suggestions. Buy anything that is whole food and less than $1 a pound net weight. Potatoes are entirely edible, so that’s a good deal. Bananas have a peel so that’s not edible so you have to account for waste. Beans are a whole food and so are most vegetables.
I just piece things together and make meals. I use Living Cookbook software to enter ingredients and find recipes to match when I can’t think of something.