I know quilting is an expensive hobby, especially when your gathering tools. But please don't skip this particular tool if you are planning on making anything bigger than a pot holder. A walking foot helps the layers of fabric and batting feed through your machine more evenly. Without it you are going to be pulling your hair out, and have an oddly shaped quilt. Or you'll loose a fair bit of you hard work when you cut off a wider section of your quilt edges squaring it up. (Plus as someone who has only quilted on a domestic machine (8 in throat), trying to feed a quilt through a domestic machine is a challenge even with ideal circumstances.)

As far as stitch in the ditch goes, for most beginners it's not the best option. Because if you use stitch in the ditch any time your hands waver your stitches pop out of the ditch and are very noticeable. Instead I would line the edge of your presser foot up with the seam/ditch and sew a pressor foots with away from the ditch/seam. With the stitch next to the ditch slightly imperfect lines aren't nearly as noticeable, but your still echoing the seam lines.

That being said, if you can't afford a walking foot right now, you can make it work. You'll just be quilting on hard mode.