A friend of mine, the esteemed Aaron Einhorn, mentioned it made him want to bring it into a Star Wars RPG session, just to add that element into the game. Here's a few thoughts on how that could be done.
Sabaac in a Star Wars RPG
The biggest trick when incorporating gambling or games of chance of any sort into a tabletop RPG is it in many ways removes the players from their characters. After all, your character might be an ace card sharp, but you may actually be kind of crap at cards. How do you model this?
The easiest way to do this is to tie in the character's gambling roll to the actual hand of cards, granting extra initial cards to the hand based on the degree of success in the roll. The character then makes an initial hand out of all cards, placing the rest in a "gambling pile" where they sit, safe from randomization and able to be swapped out at any time.
Games with Success Levels
In games with success levels, the process for doing this is relatively simple. Have each player with the gambling skill make a roll. Remember the number of successes or success levels they get on their roll.
Next, deal each player 2 cards for their starting hand as standard. After the hand is dealt, each player with the gambling skill then gets one extra card from the deck. From these cards they make their best 2 card hand. The cards they do not choose are placed face-down next to them. These face-down cards are immune to the roll of the dice, so long as they remain face-down and out of the player's hand.
They may, at any time, be substituted for one or more cards in the player's hand. Cards which are swapped out, however, are discarded.
For example: Kalar Von has the gambling skill. His player rolls the skill before play starts and gets 4 successes on the roll. After cards are dealt, Kalar's player is then dealt four more cards. Kalar looks at his hand and sees it's not good: a 10 and a -3. Looking at the four cards he has from his gambling roll, he sees he has a -3, 7, 4 and 0. Still, knowing that there are three rounds to go in the hand, he chooses to sit for the time being and places all four cards face down.
His turn comes around and he draws: his card is a -5. He decides then to replace the 10 with the 7 from his pile. The 10 is then placed on the discard pile, Von has 3 cards left in his gambling pile, and his hand is now -1 (7, -5 and -3, significantly better than his original hand.
Unfortunately, the dice are rolled and the symbols match. Von must now swap out his hand for 3 new cards. The three cards he still has in his gambling pile, however, are "safe" and are not swapped out because he hasn't used them yet.
Games without Success Levels
In games without success levels, where the result is simply based on how high a roll the player gets, it's usually best to "create" success levels. Simply set a number above the base success, and every increment thereof is a success level. In games rolling 2d6 as a core mechanic, for example, the average roll is 7. Let's say that after adding other factors in (attributes, skills, etc.), an average character will roll 10. You would start, then, with 10 as your base success. You could from there decide that every 2 or 3 above this success grants one extra card.
In a standard d20 game, for example, your average character with +1 in an ability score and a skill granting an extra +2 will see, on average, a roll of 14. 14 would be your base level of success, with extra cards granted on a 17, 20, 23, etc.
Failure on Checks
Failure is much more difficult to adjudicate. In general, it's best to treat failed rolls as simply granting no advantage to the game--it's the same as if someone without the skill were playing. A critical failure (if your game features a critical failure mechanic) could result in starting with only 1 card rather than 2, but this will also unfairly penalize a character with the gambling skill a certain percentage of the time, as opposed to those without the skill.
A potential better option for a critical failure would be to simply have the character ante in and then fold that round, playing the fold penalty to the sabaac pot. If you choose this method, however, all players should roll a check--even those without the skill should see a chance for critical failure. Only those with the skill, however, will be able to gain extra cards, regardless of how well they roll, unless the unskilled player rolls a critical success.
Characters who roll a critical success on their gambling check (if your game has critical successes) gain an additional card to their gambling pile. Characters without the gambling skill who roll a critical success actually gain a gambling pile consisting of a single card.
Cheating is done at the very end of a hand. A character wishing to cheat rolls an appropriate skill opposed by their opponent's appropriate skill. If the cheater wins, they get to go through the deck and discard pile and select any one card to swap out with any one card in their hand. If the opponent wins the check, the cheater is caught, and it's beyond the scope of these rules to determine what happens in that case!
There you have it! System agnostic rules for incorporating sabaac (or really, any gambling card game) into your RPG sessions. Enjoy, and don't forget to comment with your thoughts below!