When i buy the players i am trying to balance my squad. And even when i challenge my friends that are 3 levels more then me (that is 4-5* more) i never lose more than 2 or 3 goals. So that means if someone challenge me with the same or even 1* better team then me, i can beat him or he can beat me with just 1 goal difference (that is if i get direct red card or a lot of injured players). Try to maximize the condition, moral and the win bonus, u will see what i mean. And yea, try to have more friends to help them because they will help u.