Dice is the best for me but is really high-risk. It is not difficult to understand so anyone can play on it and win some decent amount of profit if lucky. It can also drain your capital quickly if you hit the red lose streak more often than the green one. I've tried doing it before using a martingale strategy with only 0.0001btc starting capital, I quickly made it to 0.002btc in less then 30mins but just lose it afterwards because of my greediness.