If you want a scoring player, Jump Shot in general is the best skill to have. I would also recommend IS and driving on your SF. JR can also be useful if you want to play an outside offense.
OD, ID, and REB are also very important skills. It doesn't do you much good if your opponent can score easily.
Don't count out the importance of Passing and Handling either. I guess you really need good all around players.
For your SF, I would recommend 1v1 forwards (or guards) and OD to start. I would train handling to proficient/prominent and OD to prolific/sensational. Then train JS to prominent/prolific. Also, add in a bit of IS up to proficient/prominent. With Coleman, this could take a while, so I would settle for respectable. Hopefully, you can get there by the time he is 20 or 21. From there, keep training, but make sure you know how much salary you can handle.
A lvl 4 trainee should be a good level for you. Good luck!