There are gathering presser feet and ruffler attachments, which are two different things. Back in the 1980's we put ruffles on everything. I used my ruffler attachment to make the gathers on a folded fabric, which I usually cut 6" to 8" wide. I rounded the corners on the quilt, then sewed the ruffle to the front of the quilt, and hand finished it on the back.
If you don't have a gathering foot or ruffler attachment, you can zig-zag over a size 10 crochet thread, which easily draws up the gathers and doesn't break, like the 2 lines of basting stitches does.