A few years ago I started a new website called IMSource.org.
And I just so happened to select a premium WordPress theme called Genesis Framework.
Over time I built the site up and as a result the organic traffic began to increase significantly.
Now, originally, I thought it was due to the quality of the original content I was posting to my site on a regular basis…
However, later I duplicated the same (with the same theme) and THAT site began to rank amazingly within search engines as well.
And then lastly I met some blackhat SEO guys and they confirmed that Genesis what they used on all of THEIR WordPress sites…
So, if you are building a site to get ranked and suck in affiliate commissions, I would highly recommend investing in Genesis Framework and one of the Studiopress themes.
Also, I highly recommend also picking up Design Palette Pro to make it easy to edit and customize your themes.