A friendlies season is a 1vs1 season and you have such a season which each of your friends. If you win the first 3 matches in a friendlies season you get the achievement. Once you or your friend won the season a new season will start.
If you want to boost this achievement set the time to 2 minutes per half and invite your boosting partner. (You need him on your friend list) Just win the first 3 matches and let your boosting partner win 3 matches afterwards.
While in the match you can try and go for other achievements as I did myself, but this is up to you.