I've got two words for you: Pro Shop.

In your situation I would HIGHLY recommend against buying a used bow, especially on E-Bay! You need a qualified pro to set you up so that the bow you get fits you properly. Go to a proshop and get measured for draw length and a comfortable draw weight that you aren't straining to shoot. Shoot as many bows as you can get your hands on to find out what you like and dislike, then make an educated decision on what you want. The shop may have something used in your price range but don't buy something just because you got a "good deal", buy it becasue it fits your needs, and since you don't know what those needs are yet, get some help.

If you've got a club or even better a 3D shoot in your area go and ask questions. You're going to meet a lot of great people that are more than willing to point you in the right direction. Find the top shooters and listen to what they've got to say.