Figure out who your best players are through performance. See who does best, and see what ratings they have that are better than your poorer players.
Check all-time leaders for stats, and see what they have in common.
Don't try to overthink things, either. There's a lot of information to try to sift through, and hopefully figuring out which ratings are more important will help you to focus a bit.
And the whole mentor thing is good.... but keep asking "why", too.