Definitely sounds like you want to focus on the Sloane Gang outlaws. Dudes like Jose Morales, Benny McGill and Darragh Meng all have that gambler vibe, as does the drifter dude Steele Archer.
Outside of their Hucksters, there are other dudes like Barton Everest, Pancho Castillo and Miranda Clarke that fit with the suave gambler theme.