Social Bookmarking Money Site

Hi Guys

I'm stuck on page 2 and 3 for most of my keywords. On-page is good.
My Tier 1 consists currently of:
- 10 Tiered Web 2.0's
- 5 Tiered PBN posts
- 1 Tumblr
- Social Signals to most pages

What kind of links can I create to increase my rankings? I was thinking about social bookmarking but I don't know much about that...