I've bought some of the $1-a-yard stuff at walmart but used it mostly for quilt backing .. . . .but I have also gotten some great remnants and other fabric at walmart - unfortunately our local ones terminated their fabric departments last year.
I do buy lots at joann's . . . and I go by the feel as well as the color; and only use cotton any more.
Years ago I did use some gingham from joann's in a quilt . . . and the squares frayed loose from the stitching over the course of time. So I never ever use gingham . . I'm sure there is some that is good for quilting, but once burned, twice shy.
I've been to quilt shops . . . and I can't tell the difference in quality from joann's keepsake calicos. . . except of course for the price!