I haven't been to prison personally but from what I have seen in the movies and read from articles, I can say that its definitely not for the weaklings.
All kind of nasty shit happens in prison and gambling is just one of them. If we are not strong, we won't be able to survive longer in a prison.
Those who are addicted to gambling will have a hard time in prison because they won't have much to offer and might often end up in fights to due to non-payments.
Addicted gamblers in prison can use provisions like food, clothing, toiletries, and others for gambling if they don't have access to money. Some young exconvicts in my town told me that they gamble with dice and cards. They also said that sports games like football and table tennis could be bet on. There were always sports competitions between prisoners, so they could also bet on the outcome of games.