My recommendation is that you cover food and water first.
For food I recommend you learn about packing rice and beans in vacuum-sealed mylar bags.
Gosh, I'm working on a book that covers all this. Maybe I can make a partial version of the book available for download just to help folks get prepared (I've been studying the subject for a while now).
If I had to recommend three things to you they would be:
1. Learn about vacuum-packing beans and rice in mylar and storing them in food grade plastic buckets (videos available on YouTube - just search on 'mylar').
2. Learn about the use of calcium hypochlorite for water purification. Also, the little portable Katadyne water filter is truly excellent if you've got a budget for it. Also get 1 or 2 rain barrels set up.
3. Put back as much as you can by way of first aid. Especially antibiotic ointments. Also, read the following page closely: http://www.survivalblog.com/2010/07/a_doctors_thoughts_on_antibiot.html
See post #19
You can also make your own homemade filter if you have a limited budget. Just have layers of polyester 'batting material' and activated charcoal in some sort of PVC pipe, for example. If you do this you'll still need to purify the water produced (which is where the calcium hypochlorite comes in).