You've got a great little machine! It does need the "old style" presser feet, but you can still get a great selection.
There are 3 ways you can quilt on your 707. #1 is free-motion, which you'd need a #9 darning foot for.
#2 is with a walking foot. I've done some of my best quilting on my home machine with a walking foot. The stitches are always so even and you'd be surprised at how tight of a turn you can make with a walking foot. The price is scary ($160 or more), but I don't know how I could live without my walking foot.
#3 is the Westalee Ruler Foot and templates. I've got a woman in my Home Machine Quilting Club with a Bernina 830 (very similar to your machine), and she is really going to town with the rulers. You'd need a #77 half-shank adapter with the Westalee low shank ruler foot. Bernina makes a really great ruler foot (#72), but they haven't made it for the older machines.
It really helps to have as big a table space as you can. Your slide-on tray is good for small projects, but the bigger, the better. It also helps a ton to wear quilting gloves. My favorite is "Machingers." They fit snuggly at the tips of your fingers, and they're made with a stretchy, mesh fabric that breathes.
Have fun with your machine!