To upgrade your player, you need to play the MyCareer. The decision you need to make is which stats to upgrade. This, of course, depends on the position you play in. You need to gauge which position you play in, boosting which stats will benefit you the most, and upgrade based on it.
The game isn’t generous with VC so you need to be smart about spending it. To earn VC, you need to perform well and win matches. Once you’ve made a decision, open up the Main Menu and Attributes Menu.
Upgrading skills require you to spend VC and the amount required increases with higher stats value. A player with already upgraded stats will require more VC so try to spend them wisely. Another way of doing the same thing is by completing badges.
They are challenges that require you to complete different things. Blocking a set number of shots, the number of dunks, so on and so forth. You can work on the badges and forget about VC entirely to achieve the same results. Or better yet, use the VC to work on the aesthetics of your player.