I would also suggest that anyone wanting to sell on etsy, or any other online marketplace, targets a particular market. Think of different groups of people you can target, and then think of how you might make a pen specifically for them. Then specialise and target your marketing. Etsy attracts mostly women....so think of things women might be interested in. Lots of women like cats....maybe a shop full of pens with pics of cats on them. Lots of brides shop on etsy for unique wedding items, so maybe make pens which they can give as gifts to their bridesmaids and groomsmen (especially if you can personalise).
Once you have identified your niche, work out what social network people with these interests tend to visit most - is there a strong instagram presence, Facebook groups, etc. The good thing with pens is that they are easy and cheap to post, so you may find your main market is overseas, don't let this put you off. If you have a good quality, unique product that you have marketed correctly people will pay.
It may take a few tries to find the right niche that you can market to, but once you have, it will be much easier to sell to.
*Disclaimer* My ideas above may be crap....they're just to illustrate a point. I take no responsibility if you fail to make millions selling cat pens (though if you do make millions, I want a cut) 
