Link Earning and Quality Content
I am certainly in favour of Content. They say Content is King, and Google will love your website, if you have fresh content and it will give you great impact in rankings. Not only that, if you earn links from several high quality directories(Linking to High Quality websites is written because, I don't think Google has upgraded PR this year, hence there is no point considering PR for the quality of the website since we can not benchmark the quality based on PR), I think that would again boost your rankings and in turn traffic.
Social Bookmarking will definitely give you the back links, provided you know how to earn the value of your bookmarking's. In a nutshell, it is recommended that you create a blog with fresh content on regular intervals and you keep working on your strategy.
Thanks!