Wow! You guys are awesome. :D Thanks for all the responses. There are definitely a few things here to think about.
Since I'm still new, I don't really know which kind of quilts I prefer. I do know I want to try something more complex than 9-patch. I will have made four quilts as gifts before I make the first for me to keep, and I know that one will be a mystery/sampler quilt (I think queen sized). So I guess I'll keep buying fabric as needed for now unless I find an awesome sale on something I love! Maybe after a couple more quilts, I'll have a better idea of what I want to do in the future and will thus be able to buy fabric in advance.
Thanks again for all of your help!