If you are paying a link directory to add links to your website to help your ranking they must add dofollow links. They can't have you pay for a nofollow link on your site. There are many sites that use nofollow links if they are linking to a spam site or other type of site like this. It is a very good idea to read all the rules that Google has in place about links and how they count for your site. The article is very long and in one area it does have a detailed explanation about links. They are saying now that backlinks to a site aren't as important as before. I do believe this is because people can pay for backlinks to their site. They are looking for relevant links that add quality to your website and not links from a link farm or a backlinking website. It is best to spend your time, build relations with other bloggers in your niche and share links like this. I know it is harder to do and takes a lot of time. but in the end, this is one of the best ways to get ranked higher in Google and other search engines.