Pay X dollars for Y Mult that hand/round
#Account Withdrawl joker
open topaz
fathom panther
For that to work you would need to rework how you interact with Jokers as they are either totally passive or activate automatically when you fulfill conditions (play X hand etc). With this you'd need to actually input something for the Joker to function, even then if it's a 1:1 of gold to mult it would be quite underpowered to spend 10 gold for merely +10 mult. Even if it was 1 gold for +3 mult it would be high investment/low payout.
To try and match the theme, maybe have each purchase in the shop permanently increases the mult or inversely no purchases that turn increases mult. Or have it passively gain mult each turn but you can reduce the mult in exchange for gold, though that still runs into the problem of Joker not functioning that way.
open topaz
Maybe if it gave x1 mult additional per dollar or something like that
That might be too strong tho idk
fathom panther
In that case, the most 'balanced' you could probably do is adding X0.2 (base of X1) per 1 gold, up to a max of X2. 5 gold for X2 is somewhat reasonable, providing you have the money for it.