Go to a local feed store and you can buy raw rolled oats for about $14 for 50 pounds. It will keep for years if you put the unopened sack in a plastic trash bag, the put that whole thing an a sealed plastic trash can. (you can fit 2 50# sacks in 1 trash can)

You can do the same for cracked corn for about $8 for 50 pounds to make cornmeal.

This will suck horrid to eat so have plenty of sugar, spices, salt, baking powder, etc also stored. Either this or starve to death and I'll take sucks horrid to eat. Rotate stock on about 300 cans of solid white tuna (in oil if possible)

Always have at least a year of multivitamin/minerals on hand.