Gambaling is too risky but if you wana try i suggest you use Direct Bet and either gamble on sports or the dice.
I won't recommend dice.Dice is always -Ev And i don't know but the provably fair is not enough for players to play dice with their huge amount of money.
You can try play poker if you're good at poker or at least have skill to play poker.Also betting on sport will be good for you if you have knowledge on sport.
I have played sometime in dice on rollin and there I found that there are some tricks and some precautions for which you have to care you have to focus on the timing of red and green and so you will be able to go +ve on these dice. And you are suggesting for betting on sports then it is more good but he need to have a good knowledge about sport in which he want to bet.