Best way to gauge a friend request is to accept it then immediately look at their schedule of games. If it includes friendlies ... drop them quickly. Also be wary of friend request from players you are about to play in a cup or CL elimination game. Sometimes, these players will get you to become a friend and then purposely tire out your starting squad in a friendly with their spares.

Friends are important as Gift sharing is necessary to having a successful season, especially if you don't buy tokens.