Agree with above...I'd buy the Walking foot first...I also SID with it and put my binding on with it. I bought a SID foot and never use it because I want my fabric to move underneath and that's what the Walking foot does.
I had to buy the FM foot when I wanted to learn that but that came much later when I figured I'd stitch with it and learn FM. Still not very good at it but still give it a try now and again.