I was not very familiar with online casinos before I joined the Cpayscom2 Online Casino SEO Contest, I would never imagine that people were playing casino online!
Anyway, after spending some months on the contest (and also winning second on MSN) I have learned a bit about how online casinos work but unfortunately it's not very easy to promote these type of sites.
1 - Gambling/casino sites are not allowed in almost all the major directories, you still can submit to DMOZ though... but you'll have to wait for months before an editor reviews your website
2 - Not many people are willing to link to casino websites.. and those online casino websites having top rankings most probably will hesitate linking to a new casino site.
So, the best solution I found that you can promote your online casino site is to buy links from other sites (online casino or other related) this will increase your link popularity and also your traffic if you buy links on high traffic online casino sites.