Welcome to Coinbase. First and foremost, It's important to keep a sharp eye for scams when it comes to free bitcoin. Though if you look around, the bitcoin community has a lot of great ways to find bitcoin giveaways, incentivized games and even incentivized participation in discussions or other activity.
Many bitcoin users have developed a great tipping culture. Some forums have a very active group of users who tip for informative or engaging content. You may even find places around the web that will pay directly for submitting content or articles. Also, for more on tipping here on the Coinbase community, check out the following article:
I would say to evaluate what skills you have and look around on bitcoin Job boards, and offer your time even if it's just a little help here and there. You will find people will be generous when you reach out and offer your help. Tipping is not a guaranteed source of income but a very viable way to receive small amounts of bitcoin without buying it.