I have several players on the verge of getting their next star (either at a x4 or x9 quality ranking).

For each player, I have probably applied 3-5 skill points only to NOT get them to that next star.

What is the trick to get them to that next star? Apply the points to their position strength... i.e. build up a defensive players' defensive skills or spread out the skill points and balance out the defense, offense and physical/mental skills?

Also, what is the best way to improve a GK? Apply skill points to defense and physical/mental or balance them out? I don't see the point of applying skill points to a GK offensive skills.