I use 100 weight silk thread and a Microtex size 60/8 needle for machine quilting on my home sewing machine. I quilt with 100 weight silk thread almost exclusively now; it looks so beautiful I can't bear to use cotton. The 100 weight thread comes in 1000 yard spools which are a bit more economical than the 200 yard spools, especially if you are working on a big quilt. How much thread a quilt take depends ... on the size of the quilt and density of the quilting....
I'm not usually able to measure, but I recently quilted an 18" square class sample, densely, with silk thread in the needle; I estimate it took ~ 100-150 yards of 100 weight silk thread (half, or a little more, of a small spool).
I recently posted photos of 2 small quilts, they were both quilted with silk thread.
Diane
(also a student of Diane Gaudynski's)