Yes It is possible to earn money by playing FIFA and betting on it, but it is important to note that there are risks involved. Betting on video games is a form of gambling, and like any form of gambling, there is always the possibility of losing money.
The most basic bets you can place on FIFA gambling sites. Just pick the team that you're sure is going to win the match, enter your desired stake, and place your wager. If your team wins, you win the bet they don't come any simpler than this! If your team loses, however better luck next time!