gambling over all is a sin, depends in which religion if you are Christian, a true one, then you shouldn't play any game when is money trading.
Now remember when Christ took a strike on the money traders which were in front of the temple, another thing is that those who are "silverlovers" or in translation people which have greed for money, they will never receive holy spirit, as they are looking for material goods, not spiritual goods.
Everyone should take what think is the best for him, is not some big sin, there is rule to not do bad things to anyone as you dont want the others to do bad to you.
Respect everyone and help if you can, poker is not that big to be qualified as a death sin for your soul, as you will live by his rules and help other people when they need