You have a good collection already. I started with white, beige, black and grey which I piece with and started my quilting with; then for quilting I added the primary colors of red, blue, green, yellow . Then I branched out with the blended colors of purple, orange, etc. After 20 years of quilting I still keep on hand the neutrals along with a light, medium and dark of each of the primary colors. I have found that this works for me in matching my thread to my fabrics when quilting.