Aim for an Advanced Trainer with a weekly salary between $12K-$16K per week. Very good salary for the trainer. Getting one with a specialty can be a bit expensive so unless you get lucky, it's not worth spending a lot of money on until your players are more seasoned. Look to change your arena prices to sell out or come close to selling out your arena. That will drive up your income a little. Try to settle on 12-14 players on your roster. Make sure you have 4-6 18 or 19 year olds to train each week. Make sure they play 48 minutes at the position you're training.
A good tip for you looking for trainees on the transfer list is to pick cheap 18 year old with at least average/respectable outside defense for guards or average/respectable inside defense for the bigs. B/c training defense takes way more time than training offense. So get guys who start out with decent defense.