I am confused, so you finally settled on the fact that you will get 3 trainees next season with mvp potential or higher. MVP's with good starting skills are at least 500k+ each. Its the 55 tsp below ones that are usually cheaper. I am assuming you will stick to single position training. But you also ask if you should train 1on1 first which is really 2 position training. So you dont mind giving the other training minutes to your other players? Training plans should be dependent on the skill set of the rookies you get. Which is still next season if I understand you correctly. Safest trainer level is 5 advanced. It's not too expensive to acquire and reasonable to pay weekly even for a div 4 team. If you train the players well and get consistent 48 minutes a week avoid stamina and ft training they will probably make your country's u21 team if they are defense oriented.
Everybody has given his 2 cents, best advise I can give is to look for good trainees first then formulate a training plan on the skills you want to develop. Try consulting your national coaches by copy pasting their skill set next season. Many factors are critical to training efficiently, height will help you in inside skills but will also penalize you for OD.