You can search online for information on how much food to store per person. Most often I see advice that says we should store a weeks worth of food per person. I tend to think we should store more than that amount. The Mormons believe in storing a years worth of food for their families in case of job loss, or other life emergencies.
Already prepared meals are available that are very convenient, but these are the most expensive foods to store.
|MRE - Meal Ready To Eat|
There are quite a few places (including Costco) that sell dried foods that are packaged for storage. This is also an expensive, but convenient option. I like to dry my own fruits and vegetables and store them in jars or other heavy duty containers (think rodents). Remember to store extra water if you plan on reconstituting dried foods, plus you will need a way to cook them.
I prefer food that can be eaten straight out of the package without cooking. It takes less energy to eat food straight from a jar or just lightly heated. Some of the store bought items I can recommended are nut butters, crackers, canned meats, and canned vegetables. Watch for sales for the BOGOs (buy on get one) and don't forget the condiments. Some ketchup or mustard can take a meal from unappetizing to decent.
The most economical way to store food is to home can or dry food you have raised yourself or purchased on sale. Canning jars are reusable; you just need to buy new lids. I find that home canned meat and vegetables taste very good and, in a pinch, can be eaten without heating.
Once you have your food supply built up make sure that you rotate it out. This means that you use some of the food each year and replace it with new food. That way your food supply will always be fresh. Check your stored food several times a year (once a month is best) for insects, rodent damage and other damage. Better to catch it early than find out that your hard earned food has been ruined when you need it the most.