Buying 50 sites was not a good idea, but those sites can still be ranked. You need to buy better gigs than just social bookmarks. You need some Web 2.0 pyramids and High PR links.
You need content + backlinks, that's about it. Slowly hit your sites with a variety of backlinks. High PR blogposts, High DA/PA Blogposts, Niche blog comments, Niche blogposts, PAD submission. Did you think you were going to rank these sites with just a few social bookmarks?
I hope they're not all on the same server, same IP, etc?