mate - dont bother with stamina til you have the nucleus of a squad you want to keep...it honestly has no effect (that ive seen) on performance.. maybe on final ratings but my players have no stamina (max inept) and i dont care.
FT again nah.. if you have 8 players who you want to keep great if not skip it for now.
The above 2 to my knowlege train the same speed at any age.. given this and the fact the other skills train faster at the moment then why bother??
Go for the positions based on the trainees you secure yourself. I always train 2 positions and try to get 5 or sometimes 6 people the right minutes.. whilst you are accumalating your trainees you will probably stagger starting with 1 position (so PG or SG or C) then as you get your full range of trainees then this will open up more training regimes...
Stamina IMO has yet to be implemented correctly.. if a rule change effects me for the worse i will just suck it and train it for 3 weeks.... until then its burgers and fries all the way if they can keep scoring as they have been!!
Good luck