I only bothered with the Dice poker chain once in my playthroughs so I'm not exactly an expert. The GameBanshee walkthrough isn't entirely finished yet (not by any lack of effort, I have great respect for the insane amounts of information on this site)
Anyway! I found this link:
A Game of Dice - Witcher Wiki - a Wikia wiki
To be on the safe side you could just visit and beat all these players you can find in act 3.