The following may be considered basic foundational categories for preparedness. The entire process of prepping and preparedness begins with basic ‘ingredients’ to survive and stay alive.
Each of these are relatively inexpensive to purchase for storage, they store easily for long periods, and they provide a foundation for adequate calories and nutrition to sustain life.
For those beginning their preparedness, FOOD is typically first.
Other than water (actually #1), ‘food’ is practical to start with for general preparedness.
Note: Learn what to do with the basics. Most folks don’t. For example, learn how to mill your own flour from wheat. Learn how to make a loaf of bread without a bread maker. Learn how to make foods from their basic ingredients. Learn how to garden for food.
Note: Store what you eat, and eat what you store. Integrate your storage foods into your regular diet. Learn to eat foods that are not ‘processed’. Not only is it healthier, but learning to ‘do it yourself’ will better prepare you.
A person can actually survive on ‘just’ water for weeks, and although while not eating any food you will become weaker and weaker, you would live (for awhile). On the contrary, without consuming any water whatsoever, a person will not survive much beyond 3 days! Apart from the air we breathe, water is the absolute basic ingredient for life. Water is fairly easy to store, so get that taken care of… Discover alternative sources of water in your area (just in case). Consider additional preps to treat and purify water for safe drinking such as boiling, filtration, or chemical treatment tablets, regular bleach, etc..
WHEAT / WHOLE GRAINS / RICE / BEANS
These are considered essential items for any food storage program. Adding wheat to water provides nutrition and survivability. Grain has ~indefinite shelf life if stored properly (decades+), and a flour mill provides the ability to increase the utility of wheat (into flour). Use for cereal (cracked grain), soups, breads, or even non-yeast breads such as sourdough and tortillas. The combination of rice & beans provide high levels of protein and essential nutrition.
SWEETENERS / HONEY / SUGAR / SYRUP
Sugar stores indefinitely, and Natural Honey is probably the best form of sugar because it is higher in nutritional content and has healthier attributes (even medical attributes). Sweeteners are also preservative for fruits and vegetables. Sugar is high in calories (good for survival preparedness).
SALT / OIL / YEAST
Salt stores indefinitely. It is essential to chemical action in dough and is a preservative for meats and vegetables. Oil is essential to general cooking and baking, and is very high in calories. Yeast is essential to baking.
POWDERED MILK / DAIRY PRODUCTS / EGGS
Powdered milk stores well, up to 4 years (longer if professionally sealed). It provides a source of protein. It enhances the flavor of wheat and breads, and flavors well with cracked grains and whole wheat flours. Got chickens? Then you got eggs…protein.
Organic Heirloom seeds for self-sustaining food crops. You can use the seeds from this year’s crop for next year (this only works well with Heirloom seeds).
There are lots and lots of additional categories but I feel that these are a good foundation to establish basic ingredients on which you can build.