There is a misconception that Google doesn't follow no-follow links.
Google's algorithm isn't focused on webmasters, it's focused on it's users.
Yes, a do-follow link is worth more than a no-follow but that doesn't mean a no-follow doesn't add authority to your websites link profile.
I've ran a study on this and discussed with other SEOs and our findings show that Google does track your nofollow links and you will still get a bump from them. If you buy links or build them yourself, a solid mix of do and no follow's is good.