Martial archetype : The Gamester
Gamesters are fighters that use their fighting skills to push encounters into states of gamble. Chance greatly affects these fighters, though not all of them are aware of it. Everything is a game of luck; and Gamesters often force lady luck's hand.
Cross and Pile
Starting at 3rd level, you can use this feature before knowing the outcome of a contest roll, skill check or saving throw to choose a coin's side and flip it. If it lands on the chosen side, add 1 to your roll (this becomes 2 at level 15). If not, subtract that value from your roll instead.
After flipping your coin, you can choose to do so again. If it lands on the same side as the first flip, it's effects are doubled. If not, it's effect is removed.
Game Fanatic
Beginning at 7th level, you choose one favorite game from the Favorite games list and gain it's feature. You gain an additional one at levels 10 and 18. When gaining an additional game, you can also choose one of your favorite games and replace it with another.
Additionally, you gain proficiency with a gaming set if you've played a Tavern game with it at least once.
Passe-Dix
At 15th level,, after failing a skill check or saving throw, you can use this feature to choose High (above 11) or Low (below 10), and roll 3d6. If the result matches your choice, you can consider your roll a natural 20. If it matches the opposite choice, you consider your roll a natural 1. If the result is 10 or 11, nothing happens. Whenever you use this feature, you must use the result's value for your roll.
You can use this feature a number of times equals to your Charisma modifier. You regain all expended uses after a long rest.
Lucky Break
Starting at 18th level, your simple presence can affect other's luck. When you are hit by an attack, you can use this feature to roll a d20. On a 15 or higher, the attack misses and is considered a natural 1.
Once you use this feature, you must complete a short or long rest before doing so again.
Favorite Games
Blackjack
Cards are an extension of you . You can attempt to craft a fighting deck by expending a deck of cards and a piece of ore during your long rest. The deck is a special simple melee weapon. It deals 1d6 peircing damage and has the thrown(10ft/60ft) and finesse property. When you throw a card as an attack , you ignore partial cover and 3/4 cover as you arc it's path. Every fighting deck has 13 cards . Before throwing the last card of a deck as an attack, pick a number from 1 to 4 and roll 1d4. If it falls on your chosen number, the attack is considered a critical hit. Thrown cards cannot be retrieved. These decks cannot be used to play Tavern games.
Thimble-rig
You can't stand losing. You always set the games' rules so that you have the upper hand. Whenever you make a second coin toss as part of your Cross and Pile feature, your first flip's effects are removed, regardless of the second coin toss' result. When you roll as part of playing a Tavern game you know or performing a Favorite game, you can do every required rolls twice and pick any of the two results.
Roulette
You rely on luck to make your hits more effective. At the start of your turn, you can use this feature (no action required) to call a number from 1 to 6 and roll 1d6. If the result matches your called number, you can add your Charisma modifier to all of your attacks' attack and damage rolls until the end pf your turn.
Backgammon
You mentally prepare to move audaciously, putting faith in your luck for your success. At the start of your turn, you can use this feature (no action required) to roll 2d6. If you roll a double, add 5 times your roll to your movement speed, and have advantage on acrobatics and athletics rolls for the turn.
Bluff
Bluffs and trickery become your tools. You can trick a creature into briefly turning it's attention towards you. You can use this feature as a reaction when your target is being attacked. The target must win a contest roll between it's Wisdom (Insight) against your Charisma (Deception or Persuasion) or the target loses it's reaction and the attack against it has advantage. The target adds 2 to it's contest roll for every time you've used this feature against it within the last 24 hours .