My answer is a little different than those of the others. I'm fairly new to machine quilting, too. I recently used my Pfaff Passport with the built in "walking foot" (called DST???) to machine-quilt. I had uneven stitches, too, which I chalked it up to my lack of technique. An unsatisfactory answer, since I've been garment sewing for three decades and am firmly familiar with using a walking foot. But quilting takes different techniques, and I confess to not having mastered them yet. Foolish not to do otherwise.
My advice is to invest in the walking foot. And practice, practice, practice your technique. That is, do several practice runs with the materials you are using in your project.