As you already guessed, it depends on the casino program you sign up with. They all provide a different level of statistics, varying from very little (total click thrus and bottom line dollars earned) to very much (individually tracked user ids, where they came from, what they play, how much they spend, even demographic information). Some programs allow you to set up unique trackers that you can place on each of your sites, which will help you get to the information you are looking for.