Moving around does not change or add anything. Is necessary when there's need to do so, thats only when it will change the player's greatness. Players should know when is time to Leave a particular club either prove his greatness or to improve himself. Messi's case is a clear example of one who doesn't need to move anywhere to become great, he is getting better attention in his present club and moving out of his current club might be disastrous to his career.