Hey bro,
Player 1: It's a pity he's 19, but he'll still make the U21 team when he's 21 and probably the NT if you train him good.
After 1on1, he needs a bit of passing, I like to get those up early as they are key. Then go onto inside skills and carry on with that. If you want a PF train OD and JS when you can.
Player 2:
He'll make the U21 team, but not the NT. If you have a free space train him. Get his IS and HA up. Then go onto ID and RB.
Player 3:
ID is great, most likely player out of the 3 to make the NT. Get DR, PA and IS up. Then go onto Inside Skills (IS,ID,RB, maybe SB).
If you need anymore info see the offsite.