If you have a lot of free time, you can use your smartphone to earn satoshis which is the basic unit of bitcoin. Just try some of the legit bitcoin faucet like
1. Bitfun http://bitfun.co/?ref=B41A7C9A4B43
2. Moonbit http://moonbit.co.in/?ref=70c225c75c4e
You'll earn just small amount of bitcoin when youre just starting but you only have to do it during your free time. And the value of bitcoin keeps rising so that small amount may be something after a few months