many people purchase their fabrics from Joannes and Walmart- they still make nice quilts!
visit a few local quilt shops if you have any around you- compare fabrics and buy what you like. if you don't like the fabric you will not enjoy working with it.
joannes and walmart both (at times) have some nice fabrics- others not so much-
to start buy 100% cottons- you will find them easiest to work with while learning.