Unique content always play big role in SEO link building, So, prefer first content marketing (Unique content help in on page also but here i am saying about off page works) then you can go with resource link building, If applicable then list at ecommerce market places like amazon, etsy etc. Other link building processes are near about same for ecommerce site like local SEO, broken link building, guest posting, press release distribution, participate in related communities etc..