IMO, buy what you can afford. Feel the fabric. I have bought excellent fabric at Joann's and crummy fabric at a LQS. And the other way around also. Years ago I was going to a sampler class and they give you just enough fabric to make a block and no room for errors. Well, after going back a few times and begging for a scrap of fabric, I decided to go to Wal-Mart and buy a fat quarter bundle. I believe it was 8 fq for $5. Used that for practice blocks. Wound up with enough practice blocks that I made a quilt, backed with fleece, for the kids play room. This was about 10 years ago and it's still in great shape. It gets tossed around, dragged on floor, one son even took it camping with him.
So, just look and feel the fabric - that's the best thing about shopping for fabric anyway!
Here's a website for excellent fabric:
http://www.marshalldrygoods.com/
I have never bought online from them, but have been in their store. It's well worth a detour through Batesville, Arkansas to buy from them. Just make sure you have time to just browse! My DH needed to go to Arkansas and took me with him and made the detour through there. He found a nice bench to sit on.