I always think rail fence is a great first quilt. For a second quilt, I would recommend log cabin. These quilts don't require matching seams, which is the most difficult skill to acquire IMO, but let you practice all of the other skills -- accurate cutting and sewing, making a sandwich, basting, quilting, binding. For a third quilt I would recommend a largish 9-patch, which requires matching seams. Fourth quilt would be Warm Wishes, which requires cutting up a 9-patch and matching even more seams. After that, anything goes!