**** Update ****
I just wanted to add to the part regarding keywords and learning which one might be important for your shop.
Think about the keywords you get the most traffic for. Those words can represent opportunities. If you make things with that keyword, maybe more more, increase your selection.
For instance, in my shop, i get a lot of traffic for Buddha Bracelets and when I look at sales it's a high percentage of my sales...so i'm adding more.