Hi there
If you are getting your site(s) off the ground and haven’t got terriffic traffic going, I would avoid a CPM (Cost per Mileu / cost per thousand impressions), and opt for a CPA (Cost per acquisition) deal. You would be shot in the foot by the poker room in this scenario.
However, if your site(s) are pumping traffic due to great SE (search engine) ranking or marketing effort of yours, CPM becomes an option.
If your site is in between these two worlds, I would still opt for a CPA.
Best regards
Brad