Gym likely helps with a pop or two per season but not much more. I've had a level 3 since it became available and trained Ras and Askew up from 18-23. In 5 full seasons I can probably attribute 3-4 pops to the gym alone and 4-5 to YT...
2x NBBA Champion: S55, S56. 3x USA Cup Champion: S54, S55, S56. WR for longest home streak ever at 11 in Season 47.