I have 4 boys and other than sewing an occasional baby gift for a girl (and the gifts don't all have ruffles) I didn't see the need in a ruffler. I've heard other women that absolutely love their ruffler attachment for their sewing machine, so if you have one use it, if not you can still make great ruffles. (Not sure what they cost, but even if it was cheap, I didn't see me getting my money's worth out of it.)
But I do make an occasional ruffle and here is how I do it...
I get a length of fabric (1 1/2 to 2 times as long as what I will be sewing it to). Hem one long side. The long side that isn't hemmed I do a basting stitch about 5/8" away from the raw edge.
I then do another basting stitch right next to the first one, this one I sew 1/4" away from the raw edge.
Then I separate the bobbin threads from the top threads and begin to pull the bobbin threads (both at the same time).
It will cause the fabric to scrunch up or ruffle.
I continue sliding the fabric down the bobbin thread (or pulling the bobbin thread) until all the fabric is scrunched up.
I then lay it next to what I plan on sewing to. I gently pull out the ruffle I just made so they are the same width and begin to evenly space the ruffles.
When I sew it onto my item (diaper edge, bottom of a dress, skirt, or top, bottom of pant legs, etc.), I sew it between the 2 basting stitches. (After ruffle is secured onto item, remove basting stitches.)
There's how you make a ruffle. Now, go make lots and attach them to everything and then send me your pictures (or link to them in the comments section). By the way, did you know I love comments? I do, I do, I really, really do.