Which Social Media Site is best for SEO Traffic?

I would say Facebook because it has the most amount of users but unless you pay you don't reach all your fans anyway.
Therefore I would say Google+ comes in close after that for the amount of people they have, you can reach all of them through Google+ circles, groups and communities.

 

I would go for Pinterest and Instagram.
I believe fashion niche will be more effective on image-based social media platforms.
It'll help you to showcase more of your products.

 

I'd say IG is great advice, even pinterest. Why?

Not necessarily SEO, bur organic traffic.

Because you said you were in fashion. Fashion is very visually oriented, so posting engaging photos, or unusual styles will draw people in, and if you can get them curious, they will find your link.

The SEO will be helped as well, but you won't get a boat load of backlinks. You will get nice social signals though.

Just my 2 cents, hope it helps

 

For getting more traffics for website these social media sites helps a lot.
Facebook
LinkedIn
Google Plus
Pinterest
Tubmlr

 

Google.com will help you about the question

 

Facebook, Twitter, Pinterest and G+ is the best social site to drive heavy traffic to your site.

 

Yes, Google+ is not bad either. In fact, few months back I was getting more traffic from Google+ than Twitter or Facebook. I appreciate your response. My intent was not to stir up trouble, but merely to help. I hope my comment was helpful.