No matter what you do, it all starts with practice. Practice your skills, become good, better and one of the best at what you do (whichever game you play). Play online and if you feel you're good at it you can earn money by :
1: There are various websites like Twitch.tv where you can stream "while you play" and get money. It's like instagram for gamers. You play, make followers who want to watch you play and earn money.
2.You can also start posting reviews for games you play, what you find good in them, what you like and don't like, what you wish could be improved etc. If other players\gamers find what you say to be interesting, they'll follow you and as your views grow, you'll get more money. It's a slow start and takes time to build to a level where you earn a good amount of money.
3.The fastest way would be to take part in online gaming tournaments, play well and take the prize money.
I'd suggest doing all of the above in parallel. Winning an online tournament adds to your resume and you can flaunt it on your accounts (youtube, twitch etc).
Pawan recommends the following next steps:
- Explore sites like twitch.