First player needs driving, perimeter defense and some jumpshot... I would start with 1 on 1 for forwards.
Second player - I would mainly train OD here, he also needs some jump range and handling.
Third player - jump shot, jump range and perimeter defense to make him SG while you train outside skills.
When to stop... hard to tell. I'd say you pop their outside defense 3 times and then decide what to do next. For the 3rd guy, I think he could become best of all 3. When you switch to inside skills, he will be really good and then you decide whether he's good enough to stay or you need money.