Can you in any way walk away from this endeavor with mastery AND with more than ~6000 gold? Through exceedingly numerous(I believe more than 20) trials I have discovered this to be quite an impossible feat! That being short of killing him or taking several hours to rob him, a piece at a time. Also... I didn't manage once to achieve mastery with the 2K stake. I don't know if its a bug, or by design, but I would like an explanation.
I've never mastered gambling without losing a few tenthousand gold as well. Basically, you need to get to a point where you win a streak. Gold isn't much of a problem in the game anyways - you can always gain more gold.
I'm assuming that he's near the beginning of the game - or he could just steal Ristezze's key, and daily get around 700-4000 gold. The trick is to not have the chest on the screen while passing the time. Note: Boat selling glitch?
I haven't played the game in awhile, but there is this one part in which you can buy a boat. I believe it's to take to Thantos. But you can sell it back to the captain unlimited times.