Earning with gambling is depends on your luck factor, there is no fixed income you can tell. Some day you can win thousands of USD, another day nothing or loss everyhting you bet it all depends on your luck.
That is true about the amount you can earn with gambling, no matter how long you are a gambler or you have a lot of experience. But if you are not lucky at all then you are going to lose. Unlike those newbies that have a very lucky aura they can earn as many as they can base upon to their aim on how long they are going to gamble.