thanks and welcome to BHW as this is your 1st post on the forum 
You can go for forum profiles, social bookmarking, directory submission , etc as tier 2 backlinks.
Apart from this you can build social references which acts as backlink validators, so the domain gets shared on FB, Twitter and Google plus and variety of other social platforms to show more natural viral behaviour along with organic backlinks which are being built.
All The Best !!!
Cheers:drinking2