Bree123

Another vote for light-medium grey in a 50wt thread -- Aurifil is a great option because it is 2-ply (most threads are 3-ply) so it shows up even less. It will blend in the most & not show much (which seems to be what you want). If you want the quilting to show, I'd go with a bright orange to create a triad color scheme.

I'm not sure if your comment means that you don't want to do much FMQ & need to keep it simple -- in which case, I'd suggest either a basic meander because no one will even know if you mess up since it's meant to go every which way, or you could just do a stitch in the ditch following around the pieced curves. As long as it doesn't bug you a lot to ccasionally have a stitch or two outside the ditch, I must say that I personally find FMQ "in the ditch" to be probably the easiest stitch pattern there is for FMQ.

If you are completely opposed to ever trying FMQ, you could try going slowly & following the curve with your walking foot. You might even try a zig-zag stitch so you don't have to be as precise. Or, you could do a wonky crosshatch where you quilt through the center of the "pie piece" the one direction & quilt from the edge of the curve to the edge of the curve the opposite direction. Quilt the solid squares in a traditional crosshatch or however you like.