this is a very interesting question. I've just opened my shop and registered both an instagram and pinterest account. So far (with only six listings in my shop) I've found instagram to be more active, altough I suspect many of the likes I'm getting are kinda spammy and automatic.
Pinterest I believe needs some time to take off. I'm trying to engage as much as I can but I haven't had a single repin or like so far.
I'd love to hear some tips from people with more experience.
My shop has been open for about a week. I have posted my items on Pinterest and my shop on Facebook. A lot of view from FB, but no repins on Pinterest.
How much time do you spend promoting? Did you create a shop FB page?
The more present your shop is on social media the more chances new people and therefore potential customers will get to see your work or products. So...yes, create a facebook page for your shop, twitter account, instagram and pinterest.