Hi @Arnab3,
What do the social media links look like in your case?
Do your promo banner links have corresponding URL parameters? e.g. domain.com?promo=5
In this case you can create your audience with site page attributes.
Or is it more in the direction of user comes from URL xyz.com/abc to domain.com
In this case you could create your audience with referring landing page domain/query/URL (Traffic Sources).
Best regards