SusieQOH,
I use Isacord which Leah uses. It’s wonderful. I also use Glide. It gives a bit of sheen to the stitches ;it makes your fmq look rich. I also use Superior micro quilter on busy fabric where I don’t want the quilting to distract from the fabric.
EXperiment with different threads until you find what you like. Remember to pair your needle size with the thread weight.