If you are just starting out I think you would be bettered served by buying in smaller quantities. In stead of buying 50# of rice and 50# of beans buy them in 2#, 5# and 10# bags. I large use popcorn tins, they will hold 2 10# bags of rice, 16-18# of mixed bags of beans and 15-18# of mix types pasta.
The smaller quantities will allow you to stock a greater verity of food stuffs. A number of 10# bags will take less time to be used and replaced then one 50# bag giving less tome for it to go bad. Dollar general store has 10# bags of rice for $4.75 whereas the grocery stores here are asking $9.00+ for a 5# bag.
Different kinds of beans taste deferent and are prepared in deferent ways so verity will improve your quality of life postSHTF.
Allways look in the ethnic section when you shop a lot of times you can get the same food for less money. Some times you can find food that you will not find any where else such as Klass drink mix and spices.
Look at it this way if you were to go out today and buy 50# each of rice and beans and the bubble popped tomorrow, how long will it take for you to get sick of just eating rice and beans?
I buy my food by the day. Lets say I have X amount of rice, beans and pasta then I figure out what I need to buy to add to it to turn that into Y number of days worth of food then I start over with rice, beans and pasta add to it until all of would be use up and so on. It works out so that each 30 day worth of food that I buy completes a cycle of food buying.
All of the food that you buy needs to be marked with the date that you bought it so it can be rotated.
Some day when I get time I need to post 30 days worth of recipes and a list of every thing that you need to make them. You also need to stock ready to eat foods the last thing that you need to do when fending off an attack, are sick or trying to get a crop put up before it goes bad is take a time out to cook a big meal.
Wheat and beans take years to go bad if packed properly. Buying canned goods or 2 and 5 and 10 pound bags is much, much more expensive than buying 50 pound bags from the right places.
Some grocery stores will sell in large quantities, but generally this is at a hugely inflated price. I buy 25 pounds of beans for about 11 dollars. I see the exact same bag at the store for 30. Costco is not so bad, but (at least here) they don't sell much more than rice, wheat and oil.
Buying a variety of things is important to stave off appetite fatigue, but buying a large quantity (say a year's worth) of the basics is a cheap, easy way to stay alive if food supplies are not available. I think the best advice there is to store up on the necessities, then add more variety to it.
You make awesome points on rotation, dating food, and shopping the ethnic section. I'm always so amused to see Corn meal go for 4 dollars and a larger container of Masa de Harina go for 3 dollars.