I tend to buy blenders - fabrics with small prints that "read-as-solids" - and have huge numbers of them across all value ranges in my stash. From these, when purchasing mid-1800s repros, or 'modern' big prints, I can pull all the complimenting fabrics I need to make a quilt.
I also have reproductions, stripes, solids, geometrics, florals, and some theme fabrics in the stash, which is fairly equal in amounts in all colors.
Jan in VA