It's definitely not an actual game - it's just a way to throw away money (something that exists to take a jab at the ridiculousness of gambling, because at it's core, this is all blackjack is - throwing money at a 46% chance of doubling it).
Here's the thing you may be missing though - your event actually has a 100% chance of making the player money.
1) Save Game
2) Win money
3) Lose, Reload Save
4) Profit!!!
That may seem like a small thing or something you can ignore, but if money is going to affect your game's 'balance' at all, you can't. If you make the gambling part actually fun and one where the player tends to come out ahead over time, they'll enjoy it and play the game. Otherwise you have to be sure the rewards are small enough that actually making enough money to break the game takes a long time. Dragon Warrior (Quest) IV did this really well.
Edit: To do it one event you "nest" the conditionals
>Self-Switch A=True // playing
>While Self-Switch A=True
>Player Gold < 50
>>>Yes?
>>>>>>You Can't Play
>>>>>>Self-Switch A=False
>>>End Yes? Block
>>> Else
>>> Would you like to play?
>>>>>>Yes?
>>>>>>>>Lose 50 Gold
>>>>>>>>Generate Random Number
>>>>>>>>If Random >54?
>>>>>>>>>>>>Yes?
>>>>>>>>>>>>>>>Win - Add 100 Gold
>>>>>>>>>>>>Else?
>>>>>>>>>>>>>>>Sorry, you lose // Ends Random>54 block
>>>>>>>>>Play Again?
>>>>>>>>>Yes?
>>>>>>>>>>>>End // goes back to while loop
>>>>>>>>>>No?
>>>>>>>>>>>>Self-Switch A=False (no longer playing)
>>>>>>>No? // would you like to play?
>>>>>>>>>>Have a Nice Day
>>>>>>>>>>Self-Switch A=False
>>>>>>>End No? Block
>>>End Else Block // Player Gold < 50
>End While Loop
Self Switch A=False //failsafe code - not strictly necessary
I think that's got it. Indentation your friend, you'll be able to see and keep track of your code this way, just step through it like a flow diagram. The event editor is really good at helping you keep track of things like this.
Honestly, you could do a "real" blackjack game using events but that would be a LOT more complicated and more than I could show you in a forum post or three.
Edit - I did a 'quick and dirty' version in the event editor.
BMP's attached since I can't remember how to post screenshots
There's the basic jist of it. There's a few extra lines and loops just for clarity and to help with tracing the logic out.
One.bmp
Two.bmp