Actually there's a lot ways to earn bitcoin there are full of risk and there are not but not that profitable. Here are the some way to earn:
*Investment
*Trading
*Bounty and Signature campaign
*Airdrop and more.
The only things I enumerate are the ways how I earn bitcoin. For now I currently unto long term investment. I am the kind of person who don't have a time for monitoring the movement of the market all the time due to some businesses hence, I choose to hold and wait for the next uptrend.