If you haven't yet read the articles on the home page of this website (go to the bottom left of this page and click on "TLB Home"), be sure to do so. They are listed in the left-hand column of the home page and will give you lots of information on gear selection, gear lists and general backpacking information.

The general advice on this and other forums is to buy your pack last. You want a pack that's the right size for the rest of your gear (plus food and water), neither too large nor too small. Having a pack that is too large tempts you to take too much stuff (remember, this is a LIGHTWEIGHT backpacking forum). A too-small pack means you have to tie stuff on the outside which affects the balance of the pack. In addition, you need a pack whose suspension will let you comfortably carry the bulk and weight of the rest of your gear. Those with 15 lb. total pack weights can get by with much less pack than those carrying 30 lbs. It's most important that the pack fit you properly. Pack fit is almost as individual as shoe fit.

Welcome to the forum!