I came across this site where people can roll the dice, earn free bitcoins and also multiply them. How legit are these sites and how to use them effectively?
Don't earn bitcoin from site where people can roll the dice or any site which is gambling. It's not improve you knowledge in bitcoin, you should try something better like trading or mining or participate in bounty campaign. Faucet is also good, you can earn free btc from it but there are many ads that you will see and you will spend a lot of time.