Maslow made man's 'hierarchy of needs' famous by pointing out what each person needs to be a complete human being. Here's the CNI 'Hierarchy of Needs' for the survivalist:
1) Water. Without water, you would be dead within a few days. Water is basically free during normal times but if TSHTF, if you have nothing else, you may want to have some water stocked.
2) Food. You can do without most other things but you do need food. Preferably an assortment (prevents those nasty diseases such as scurvy and goiter). You can be living under a tree in rags but you do need food. Stock some of this as well.
3) Clothing. Appropriate clothing. You're going to wear something anyway so make sure it will work in a wide range of situations. Sturdy pants, shirt, shoes, socks, maybe a jacket.
4) Shelter. You can sleep outside but that offers very little in the way of protection from the elements, at least, and protection from predators, at most.
5) Things that protect your health. Such as vaccinations, soap for keeping you and the things you eat from clean, bleach to keep your environment clean, etc.
6) Things that protect you. Your own personal protection is definitely among the top things when it comes to actual needs. A gun is nice, but so is a sturdy lock for your door, a fire alarm for your home, or a sock filled with rocks or a crow bar to wield as a weapon.
7) Things that add to your comfort. This can be everything from an extra blanket to a cell phone to connect your with loved ones or the police to toilet paper.
8) Things that can keep you entertained. An iPod is nice but so is a book. Once your basic needs are met, the rest is gravy.
From there you can expand. You may want to include transportation, although your feet will work fine in many cases. You may want to add in socialization opportunities. All you really need to survive, as I have learned from countless refugees and immigrants all over the world, is really quite basic: water, food, and clothing. An intangible such as belief or hope for something better is also right up at the top of their list as well.
A step up from the basics would include shelter and things to protect/enhance your health and safety. Once the basics are taken care of, you can move on to things that aren't as critical but still quite welcome including things that enhance your comfort and keep you entertained.
On a side note, almost all of these things can be found free in our society.