I spent $40 at my LBS for their cheapest rack and I'm happy with it. I just bungee my backpack to it, although the QuickTrack system looks nice. It does lock you in, no pun intended) to Topeak bags, however.

Honestly, just check the weight limits and make sure it will work for you (mine is 25 lbs.) and that it will fit your bike. You'll learn what works and what doesn't, and you'll be in a much better position for your next rack purchase.