I will give you a bit different advise, don't invest too much in web directories. These are past and not important anymore. Website owners realize nowadays that social media is more effective than directories. Since google is fighting with websites with duplicate content, and web directories failing into this category from the nature their business, long term these directories will disappear. Why to invest into something that has no future.
you can to more and more seo and generate back links and than your site visitor will be increase and your site come up in search engine and your visitor increase automatic
Always people say back link is the important fact to improve Page Rank of site. Please keep it mind next.
I think content is what matters. Whether you invest money on marketing or not, if you have good content..you always get good traffic.
I agree with happyblog.PR is not the most important your content is attractive and have huge traffic.
Google nowadays seldom update the PR, almost 1-2 times yearly, PR is not the most important i always say, if you have an "established" quality web directory, people may pay it for listing.
More Traffic, More backlinks, high traffic = PR. Increase your do follow backlinks from high PR sites step by step. You will get PR for sure.
By building quality backlinks step by step; The best backlinks for a directory site is again from directory sites
Dear Friends, You have to need the quality back links (Link building) and update unique content and off site optimization work for your directory .
You also need to submit first your directory to the directories like blog directories, search engine directories. to increase traffic from your directory site.