Tier 1 >> Backlinks to your site
Tier 2 >> Backlinks to Tier 1 Backlinks
Tier 3 >> Backlinks to Tier 2 Backlinks
and so on
For Tier 1 you need quality , unique content, etc. You definatly do not want to use xrumer for tier 1. Build nice web 2.0 blogs, with images, lots of content etc.
Then Tier 2, for indexing tier 1 and so on, you should use like social bookmarks, wiki backlinks and such. You shouldn't just think "oh tier 2, it can be the worst quality and it won't matter".
There is a lot more to SEO than just building backlinks, you have to have proper keywords, with natural ones too, with the URL etc. You should make it look as natural as possible.
Your on-site SEO is VERY IMPORTANT, most under-estimate the power of on-site SEO.
Feel free to hit me up on Skype and I will give you a report for your website for your on-site SEO, it will tell you what exactly you will have to do to fix it and make it proper.
In backlinks, you will want a lot of diversity too, so you should not expect to rank just from web 2.0s, focus on proper quality content, lots of diversity, not spun stuff, and so on.
Luka B