There is a Blue Dot bobbin case with tension set especially for free motion quilting. I find it works like a charm. Never use the yellow dot bobbin case – the tension is too high and you will get loops of upper thread on the wrong side. Sometimes the red bobbin case works well if you use the same thread on top as on the bobbin.
My first choice is to use the Blue Dot bobbin case. Saves lots of fiddling.