With the walking foot, it was mostly trial & error -- with some phone coaching from my grandmother. I had a vintage Singer & there was only one type of walking foot I could find for my machine & no special adjustments to settings on my machine so it was fairly straightforward. I just set my stitch length to 8-9 stitches per inch (3mm)and started stitching away. If you can start on a lower loft cotton batting like Warm & Natural or Quilters Dream Request, that will make things easier for you. (yes, there are many wonderful battings out there -- my personal favorite is Warm & Plush 100% cotton, and I also like Hobb's Heirloom 100% wool, but those are somewhat more challenging to feed through the machine)
For FMQ, my first lessons were online classes with Leah Day via YouTube. There are many things you need to know besides the proper foot to even remotely successfully execute a FMQ design: drop/cover the feed dogs (usually), set stitch length to 0, how far apart to space the quilting lines, marking, speed on a straighter section vs going around a curve, how to load the quilt, how to hold the quilt, etc. I definitely recommend some kind of class for that. If you can get to a live class, that's almost always the best choice. If there either aren't any nearby or you have a disability (like I do) that may prevent you from sitting through hours of instruction at a time, there are many wonderful online classes. I've taken classes online with dozens of different instructors at this point -- plus a few live classes -- and still think that Leah Day offers
the best beginning-to-quilt classes on FMQ. Here's the link to the series that I recommend:
https://www.youtube.com/watch?v=fFcI...1F4B76430BB141