I'd like to add that if you're going to create such a cache of food its a good idea to keep other important supplies such as medicine. I don't just mean a first aid kit. Keeping a supply of basics like antihistamines, allergy meds, cold and flu stuff like neo citran (really good stuff for colds and flu, I can't recommend it enough) and nyquil and stuff like that can be very important
That said, food wise, i'd suggest supplementing any vitamins with fast growing indoor plants that provide things like vitamin c. a small bag of beansprout seeds for example, area absurdly easy to grow even on some damp paper towel next to a window, and a small amount can provide all the vitamin c you need, letting you hold on to any supplement pills for when you really need them
I also recommend freezing any bags of flour or cornmeal for a few days before storing them for longer term. It kills any insect eggs that might have found their way into the bags during processing and greatly reduces the chance of related infestations. Speaking of those two items, if you have little else, you can make both of those things stretch for quite awhile, making puls with the flour and what the natives used to call cold flour with the cornmeal. Puls is basically just adding water to flour and making a porridge out of it, boiling it with a bit of salt and oil and adding whatever bits of meat or vegetables you might have. The romans practically lived off the stuff so it'll keep you going for quite awhile. Cold flour is cornmeal thats mixed with a bit of salt, cinnamon and a bit of sugar and kept dry. When you eat it, just take a small amount, mix it with water and heat it up and it makes a sort of porridge. Or you can just add more water and drink it. Perhaps not the most appetizing thing ever but the natives and more than a few settlers and explorers made extensive use of it. Also, this might be more of a canadian thing, but you can also make an easy to store instant pea soup by grinding dried split peas into a consistency similar to cornmeal or the ground peas used for peameal bacon and just adding water and heating when you want to eat it. It'll rehydrate into a pea soup like porridge thats very high in protein. Its easy to store large amounts of it and easy to make good use of portion control to stretch it as needed
That said, first and foremost, store what you like to eat and know you will eat. As has been pointed out already, the psychological aspect is the most important and it will help a great deal with keeping your morale up to have food you are used to and like. Especially when it comes to the little things like spices, sauces and the like. Don't have any meat in storage? Store instant or canned gravy, mix with rice and it can provide fat and improvise the presence of meat in your diet
Fats can be a difficult thing to keep a decent amount of as anything but cooking oil or lard, but I do have one suggestion for it. I don't know if anyone has had fatback before. Its common in southern cooking for collard greens, beans and things like that. But anyway you can get it cheaply in many places and can pickle, salt, smoke or freeze dry it. I keep a bit of it on hand pickled and have found it can be very useful for alot of different things, and if you have to really stretch what you have, you can cut a small piece off about the size of a dime and chew it for awhile to add a bit of fat to your diet and to trick your brain into thinking you're getting more in your diet than you actually are. Doing that can also reduce hunger for at least a little while, basically for the same reason. Not the most appetizing for alot of people i'm sure, but doing that has served me well in hunting camps more than a few times
Also, if you're intending to keep well stocked, i'd suggest getting a cheap food dehydrator. They're great for preserving all kinds of vegetables and meats.
and one last thing, if you have pets, don't forget to ensure there is something in storage for them to eat as well. Especially where cats are concerned, with them being obligate carnivores and all
