So my question is, is the percentage of the rich gambling lower than the middle and lower class?
Percentage-wise you are probably right. However, amount-wise rich are spending way more than the lower class probably. Rich people are rich for a reason, they usually don't play the games that are going to make them poor in the long run. (in other words they only play the games which they are going to win) That's called mathematics. The poor are usually dumb and they think they can game the system. Each of them think he/she is the one special snowflake. 99 times out of 100 that's not true as you know. Since the poor usually own anything (hence the name poor) they wager everything they get every month and that makes them even poorer.