Flavor does not matter, presentation does not matter but the food shouldn’t make you sick, and should ideally have enough calories per day for the average person to survive (2000 kcal min).
Edit: I am not in any danger of starving or malnutrition, nor am I insolvent. I’m mainly asking this question out of curiosity on how people would approach a solution :)
For anyone lucky enough to have a WinCo foods in their area, they’re the cheapest I’ve been able to find for bulk dry goods. You can order 20-50 pound sacks of grains, beans, flour, etc., with a pretty decent discount on top of already low prices.