If you live near a city big enough to have multiples of the same thrift store, such as 3 Goodwills, you can ask if they route the craft items to one store. Here, all the stores have some craft items, but most go to a few stores. I just got a $5 bag of fabric from Goodwill yesterday. It included half of a jelly roll, 6 coordinated half yard cuts, as well as lots of FQ to 2 yard pieces and some orphan blocks. Another time they had bags of quilt shop quality fabrics in 1/2 to 1 yard cuts at $10 a bag. Each bag probably had 25-30 yards in it. But there are only 2 stores that I consistently find good fabric in.
I have also made several quilts from cheap poly/cotton sheets. A $5 twin sheet has a lot of fabric in it. For $15 you could get 2 of one color and one of another and make her an Irish Chain, which you could mostly SITD with FMQ in the open areas.