The best thing to do with DMOZ is to submit once to the best possible category, do your best to write a guidelines-compliant title and description, and then go to work building more content and links to your site. A DMOZ listing won’t make or break your site.
Guidelines for Suggesting a Site to DMOZ
DMOZ Gambling Site Guidelines
You might want to read both sets of guidelines above, as well as the description and guidelines for the category that you’re submitting to. Hope that helps.