Building Gambling Directory

I am building gambling directory at http://www.gambling-hall-online.com/gambling-directory/

The main idea is to exchange links with other sites. I hope it will be attractive for webmasters as:

– All pages have keywords at the title tag and h1
– Not more than 40 outgoing links per page.
– I will require reciprocal links to other domain – to avoid cross linking

And what about directory structure? I think it should be close to real keywords webmasters targeting and reasonable to users at the same time.

The directory is Mysql + PHP, I can change the structure at any time but would prefer to decide on main subdirs before adding links – otherwise I cannot obtain a good PR for the pages.

The main problems to me are Sports betting, Lotteries and Bingo – I know nothing about it.

Do you have any suggestions how to name subdirectories?