Here are three joker suggestions I have:
High Roller 🟩uncommon
[Gains 1 chip per card played]
(I wanted a chip scaling joker that isn't bound to specific plays)
Joker2 🟦common
[+25 chips]
(Decks in real life come with one colorful joker and a monochrome joker. This would be the monochrome one. Its pretty simple and straightforward.
Oni 🟥Rare
[If first played hand is only one card, Re-trigger it 4 times, then destroy it]
(I Was inspired by the Oni joker in Japanese card games, aswell as the violent nature of Oni)
Note that the images i have provided are merely placeholder examples of what the jokers would look like