If something isn't selling, don't focus your time making more of that thing. Pay attention to what is selling. Keep expanding, try original items. If they bomb then you have Christmas presents for your friends!
If there are hundreds of sellers making what you make, think of how you can be different. If you find a certain charm, fabric, yarn that is unique and sells well, stock up! Invest in your shop but also know when to stop and let the profits roll in. More than one month I have spent all my profits because I am having fun creating. Try reworking what you already have. Try taking new pictures.