Personal trainer if I remember well, was the best option when, your player reach the 9* and you are going to 10* -1 cone, because if you count the greens you need to train and win 100% progress (1 cone) and you do the count (if I remember well, in some cases) you save tokens by using the personal trainer in the place to buy greeens + is a direct training and you don't need reds due injuries.