I voted for Sports betting but the voting suggests dice game to be the most safest for the newbies. I dont agree to this as dice games are not the safe, they are risky one. Yes, dice games are easy to play for the newbies.
1- Not loosing too much initially - You can claim faucet from almost all dice sites and bet all day so they are not risky I feel.
2- Easy to play game - Well, I have never seen a game as simple as rolling dice and getting a number from 1-100
But apart from gambling I feel that someone with basic knowledge can make good money with cards games too as I have a few friends who don't gamble on sports or dice or roulette but they play poker all day and somehow make fine profits.