The best use for wordpress.com is for backlinks. Create blogs on related topics to keywords you are campaigning on and build up some posts on it that point anchor text links back to your Hubs and such or websites. They charge a fee to be able to monetize your blog so it's not really worth it because even after the fee you are still somewhat limited to how you can monetize.
I recommend buying a domain name and hosting service on Hostgator for much more flexibility and freedom if you are looking to have a site you are going to put money making effort into.
Speaking of which if you are at all concerned about coding and learning proper ad placement for higher conversions you need to check out my Hub on the Heatmap Theme that I use exclusively for all of my websites and is the best purchase I have made in my marketing journey.
Good Luck :)