Hint: Self Styled NBA
If you finish NBA Challenge mode with a created baller, the game will ask you if you want to join an NBA team. If you pick a team to join, your created player will join as the teams 6th man. You will also have the option to use your team jersey in the "Edit Baller" menu. Each team can only have 1 extra player at a time.

Hint: Fast Development Points
Go to Pick Up Game and set the points to "2". Once you score you get 50 development points which you can use to get create-a-player points. You get 50 points every game you win, so if you just keep doing a rematch with only two points you can get a lot of development points.