Neutrals. I love Glide. They offer a couple of starter packs.
When I first started I ordered this one and have used everything in it:
http://www.bobbincentral.com/quiltin...al-colors.html
Edited to add, I go through a lot of white and I feel Glide Khaki seems to go with a lot. It is a light gold color. I also like threads so I have quite a bit right now. I find I don't use variegated near as much as I thought I would. Nor do I use cotton as much as I thought I would (too much lint whereas with poly I get no lint.)