Base Class: Paladin
The Gambler is a Paladin who is very lucky, the Paladin feels no need for religion because of their almighty luck. Many of their skills rely on their luck.
Lucky Coin
A Gambler paladin of 3rd level or higher gains
Lucky Coin. As a bonus action you can flip a coin and if you get heads you can increase your next roll by 3. If you fail the roll automatically fails and you take 1d4 of damage. Until later levels you only get one lucky coin per day.
Chance's Grace
At level 7:
Any critical hits will be considered a normal hit against you, if you succeed in a Con. saving throw, DC 15. If you fail you still get hit by the crit and you take extra damage equal to your Constitution saving throw modifier.
Luck has Friends
At level 15:
You may share a lucky coin with a friendly creature, this will expend your lucky coin that you give them. If they fail you still get the downsides, you take 1d4 of damage.
Ultimate Luck
On any roll of a d20, anything above an 18 is considered a 20.