I use Superior Thread's Bottom Line a #60 that a previous responder told you would sink into the fabric. Also So Fine and occasionally a verigated thread of theirs when I want a variety of colors to show.
www.superiorthreads.com
I've been able to quilt a twin with just one bobbin of Botton Line. My Bernina 1030 takes it for the top stitch and bobbin. My Jem Gold and Platinum only take it in the bobbin.
Good luck.