If you're just doing a gentle wave, use a walking foot, then, if your machine has it, use a multi step zigzag. Set your stitch "length" as long as it'll go, and your "width" as wide as you want the wave (I went as wide as possible.) Because it was a multi stitch zig zag, the actual stitches themselves weren't actually all that long, and it produced a really nice wave and hid all the imperfections, without me worrying if I was being too wavy at one point and not wavy enough at another.