I have not done much gambling. The most I gambled was in the stock market and I made very little money doing that. But my grandfather made a good living at gambling. He was a legal bookie around 1890 to 1920s. He was a riverboat gambler on the Mississippi as they went up and down the river to various horse tracks where he was a bookie as that was before pari-mutuel betting. He was the "house" in these bets and the odds were always in his favor.
He had what he called "an insurance policy" which was a huge, very expensive diamond ring he bought my grandmother. In the rare instances when things went wrong and he found himself broke, he would pawn the ring for his stakes and pretty soon recover and get the ring back. This "insurance policy" kept my grandmother living well the rest of her life after he died.