My machine runs really well with Superior's SuperBobs which are the bobbins prewound with Bottom Line thread, so I use a lot of that. They come with cardboard sides on them and depending on your machine, you may have better tension by removing either one side, or both sides of the cardboard bobbin. The thread will work just fine without the sides! Because my machine has a slower motor speed, I remove BOTH cardboard sides to reduce the drag. The recommendation for faster machines is to leave on one or both of the cardboards, but I'm not sure what to use on other machines.
When I don't have a color of prewound thread that works with my backing fabric, I usually just wind a bobbin with the same thread that I'm using on the top. I always check the tension with the TOWA gauge, because it almost always needs to be tweaked when changing thread types.
The prewound bobbins seem to have a lot more thread on them than I can get when I wind them myself, so I don't have to change bobbins as often.
Also, I buy the gross box of assorted neutral colors when I go to big quilt shows, but Superior now offers you the option of your own assorted colors!http://www.superiorthreads.com/shop/pro ... zen-packs/
It's Not What You Gather, But What You Scatter
That Tells What Kind Of Life You Have Lived !