Check the gear lists on the home page of this website. They will give you some ideas.

I also like this site: Mark Verber's Recommended Outdoor Gear. It's subjective, but at least he says so, and gives lots of other alternatives, including low-budget ones.

Consider renting/borrowing gear before purchasing. And do plenty of research.

It's generally recommended that the backpack be purchased last--you want one that's the right size for your gear and a week's food, not too big or too small.