Are your friends experienced backpackers? If so, they probably have a tent or two among them, so skip buying one for now. As for a bag and pad, you may be able to rent those, but a simple blue foam pad is only about $10. Pretty much everyone starts out with one of those because they are so cheap. Better pads like a Ridgerest cost up to $40 or so and the inflatable ones can cost up to close to $200.

Bags are all prices, from the heavy cheap bags you see on eBay or at Wal-Mart for $25 up to hundreds of dollars for a light, warm down bag. If you don't know what you need or want or even whether you will be using it often, try renting a bag or borrowing one from a friend. The same is true of packs-there are cheap ones up to expedition quality packs of every size from a day pack to a huge winter pack. I would try to borrow or rent a medium sized pack. Even if it's not perfect, you aren't going that far on your first trip. Collect your gear first, then decide on a pack, not the other way around.

There are gear lists posted here on TLB (links are on the Home Page) and on many other sites. Find ones for the kind of trip you are doing and the weather conditions. My gear list for winter camping looks nothing like what you will be carrying.

You have plenty of time to sort all this out, so reading sites like this one or perusing online gear shops like REI and our other sponsors will give you an idea what is available. For lightweight gear, use the links to the left of the posts to see a wide variety of gear of all sorts.