Thought I'd share a few tips, and hope others will do the same!
When I stated here, and granted, it was my FIRST time trying to sell anything on line, I had no concept of designating a particular card for multiple categories.  Now I am getting better.  Look at your cards and think, hmmmmm, this design is good for______, but also works for_________,and that and that etc.  Different categories mean more exposure!
This is a brain snap for me, maybe for you?
Linda