There are some website that are giving free bitcoin, there are called faucets, site that are giving free bitcoin and also they have free games wherein you have a chance to win bitcoins just like gambling.
Other earner are people who are in this forum only invested their time and knowledge and patience, there are campaigne in this forum who are giving an amount of bitcoin base on the number your post and also you have to meet their requirement to be able for you to be paid in bitcoin.
Well these are micro earnings from Bitcoin and you could barely make enough of bitcoins from faucets, signature campaigns on the other hand could be substantial if you have a higher rank and so it's better you try to invest as that's the only way you could be making huge returns with Bitcoin over time.