An almost identical question was asked and answered here:
2. Fill out online surveys in your spare time.
3. Start your own website.
4. Writing articles as a freelance writer.
The easiest way is to play best microgaming slots.
If you want to add some money into your account for less effort I would recommend a website "www.idle-empire.com/" Its mainly for Gamers but everyone can use it for free.
They offer multiple ways to earn money. Complete tasks and offers, watch videos, mine cryptocurrencies, invite friends to their site or join idle servers. It's quite easy!
They offer different withdrawal methods, on one hand, you are able to purchase virtual Items, for Games like cs:go etc.
On the other hand, you are also able to withdraw cryptocurrency or diverse gift cards.
Just see for yourself it's a good extra income, especially to buy game-related content.