Hopefully when did on page seo u have selected some helpful keywords because in off page seo, you use the same keywords but in other marketing channels such as social media channels.
So if your keyword research was done correctly with on page, when u do social sharing employ the same list of keywords.
Making video and posting on YouTube with a link back to your site will make increase the site exposure because YouTube is second largest social media. For ecommerce, it can be product demonstration or customer testimonials
Social listening may also help to build a fan base. Follow your customer or your competitors followers and listen in what they have to say and reply timely.
E.g Mr B say this on twitter: I can’t find a hair dying product that last and stay vibrant color. It is annoying.
You can reply and saying I know there is a color dying solution do exactly that, you can look it up here (your product page link)
Social monitoring can help you to keep track who is talking about your brand and products.
E.g set up Google Alerts, etc.
Check your competitors too
So you can understand your market better and come up with better social strategy
Another way to do this is do paid ad. Like Facebook retargeting ads or FB local awareness ads, or FB lead generation ads
Doing Google Adwords, etc
Just my thought