If you just post items in your shop without much thought, you will definitely be lost in the crowd. Your first step can be to stand out on Artfire. Engaging pictures, good titles, and compelling descriptions can draw in browsers on Artfire. While browsing or searching, that first picture makes or breaks your views, it's all thumbnails so make sure that first picture is square, clear and gives a good close up of your item.
You also need to search out and bring in a market. Have you done craft shows and found a following? Let those customers know they can find you anytime online. Draw people in using your blog, if you interest people, they'll be more likely to check out your work.
Even if you stumbled across a unique product or niche product, you still need to get the word out there. With Google's new changes, it can be more difficult to get found in searches, so what do you do? Like I said you need to find people and draw them in. It could be a well placed ad, joining a forum about your craft helps but these are crafters, not buyers. Try looking for places where people might actually buy that product.
Project wonderful can help with ads. If you sell jewelry geared toward wedding- make up an ad, even a 125X125 square is good. You can just use a photo,or get an ad made up, PromoPixie sells a set of Project Wonderful ads for 8.50, these can be used in other places too. But the trick is to advertise where the customers are. You may be tempted to advertise on handmade sites but instead look for sites devoted to weddings, personal blogs can be very inexpensive, even free. The real trick is finding the buyers.
There may be uncountable sellers but there are also hundreds of millions of possible buyers out there. OK not everyone is going to be interested in your items. I stumbled upon making specialized game pieces for serious game boarders. This is really a niche market but they have accounted for 70% of the money I've made on Artfire. I found there was really no one else making these. Wow did I get lucky! but I still needed to reach out to this group. I actually joined a gamers forum, just to upload my item and make a post about it. This is an unusual case but the idea is the same- there is a market for your item but you need to search it out.
Go beyond just tweeting and Facebook and even your blog, those are great tools but they reach only those who already know about you. Artfire's new tools, like Amazon wishlist and Stumble, can help reach new people but don't stop there. You'll need to do some research, look for these buyers. It can be as simple as handing out business cards. I found Moo cards to be a great attention getter. they are more expensive but they let people see what you sell. I keep those cards just for face to face. I also include my telephone number on these - if only so when a new acquaintance asks my number, I have an excuse them to give them my card.
It's not easy and you may feel like it's two steps forward, one step back but carving out your place can make all the difference. Like anything else in sales, it is not easy but with some work, you won't be just another face in the crowd, you'll be the one who stands out.