In Manager mode, access the experience points menu. Near the top of the screen is an option that can be toggled if you wish to have the experience points spent automatically. Turn the autospend off. Save up until you have about 40,000 experience points, or roughly a third of a season. After that, go back into the menu where you spend your points. You can spend a lot more points in one go. This makes it easier to decide what aspects of a player to upgrade. When you have 40,000 experience points, turn on the auto spend. The CPU spends the points better if there are more to spend.