I posted on craigslist once that I was looking for some fabric for quilting. I had a very sweet lady just give me a box full :) I offered to pay her and told her that I wasn't expecting anything for free. But she wouldn't accept anything. Very sweet. So instead of looking for the deals on craigslist maybe post your ad saying that you are looking.
I also think that if you buy for just one project at a time it's easy manageable. Most people don't finish a quilt in a week so break up the purchases. Buy just the fabric for the top, you could even wait on border fabric, then batting and backing, finally binding.