Yeah, I make about double the league average in merchandise. To get the maximum benefit, and I am not sure it is worth it, then you need to draft, develop, and hold onto your own players. So it takes awhile to say the least. It also makes you give a lot more thought into when to move players, and drafting.
Obviously, they have to have good core stats, but for me the biggest thing is potential. If I am going to train them for a couple seasons, then the finished result has to be worth it. We have two teams that might have gone bot. So that should help you get someone a little higher on your list. I have to imagine you will come away with someone in your top 4. Unless, you see a steal on the TL list, then I would hold off. You can always save up, and nab someone (maybe a little better) for a late season run next year. Best of luck with your training!