It depends on how much food and how long you need to store it. Bulk food on a budget? I use my chicken feed. I just buy a few extra months of some grains from the feed store. The buckwheat I get from the feed store is the same stuff they use for the maple syrup festivals. The millet I get is perfectly edible (for people) as well. You do have to vibrate out the occasional small stone and debris. The stones settle to the bottom and the debris (plant stems and such) filter to the top. Grain seeds store for a very long time as long as you don't crack them. You will need a grain grinder to make flour from the buckwheat. Other grains like wheat, oats (rolled) and rice would supplement.
Obviously you want a variety. These bulk grain seed would help increase your supply. Canned food has a psychological effect that is important in the first few days of a situation. But I would not trust them for nutritional value. Just raw calories.
Also, store vitamin C !!! You cannot beat vitamin C for cheap health care. You will be under stress and require more vitamins, not less.