Coin Trick

You perform a trick with a coin in your hand. Fortune favors you. Any creature targeted by the spell must make a saving throw based on your spell save DC.
On failure, the creature has disadvantage applied to all throws that would affect the outcome of a game, gambit or scheme.
Creatures who are targeted by this spell are unaware of its effects. And if successful are unusually happy and congratulatory to you about your win.