...I think that any penny spent on gambling is a money the gambler have decided to sacrifice with the hope of getting a bigger amount and not because he can afford to lose it.
If you will be treating gambling as entertainment rather than as a way to earn money, then you can consider every cent you spend as a payment for entertainment, which can be compared to attending a concert or a movie. Accordingly, the amount of money spent will be commensurate with the pleasure received.