You have to win 5-6 ranked online games to get a "promotion". Playing tournaments online in World Cup mode does count towards your 10 games, however, it tracks about half of the time. So you can always go to Xbox Live > Street Seasons and it will tell you how many you have played. I won 6 (18 points) and got the achievement.
If you don't want to play World Tour tournaments, Xbox Live > Street Season will give you 3 options for searching, 5-A-Side, 6-A-Side, and Futsal.