You earn bitcoin by some assignments online.
But the most easiest i think is by campaign signature.
Or one can even earn bitcoin with bitcoin faucets.
You can stick with signature campaigns because it is a good option to spend our time and earn bitcoin at the same time by posting our opinions or sharing some thoughts to the different topics or thread out there. Bitcoin faucet is not a good idea because it is worth and a very time consuming work and it will not give you enough money to sustain your life.