I try to stick to 100% cotton fabric. Women's and men's shirts are a good source but skirts are usually a bounty of fabric if you search through the sizes. The most important thing to consider is the fabric content throughout the quilt. My grandmother's quilts were made of old workshirts and scraps. They have withstood the test of time!
Bottom line, quilts that are well constructed and use quality fabric (used or not) will wear well. One does not require a stash of fabric to create a quilt that is creatively beautiful and functional. Old blankets are my batting of choice for winter weight quilts.