Be very careful of buying links to boost your PR.

Google is very very particular about buying paid links. In fact, Google encourages people to report paid links

Why should I report paid links to Google?

Many sites, especially those buying and selling paid links, have reported significant decrease in their Google traffic when their site used and bought paid links. Matt Cutts, a Google engineer, blogged about how Google views paid links

So if you are buying links, choose those that don’t sell to pass Pagerank (using rel=nofollow or javascript to run the text link)

beware: there are tons of services that purport to increase traffic, but there’s a huge difference between hits and sales

I think if you get articles written on several keywords and submit them to article directories then they would get you links as well as traffic.