It's basically an average of 67 over your best 25 ranked rounds.
Winning money or winning matches against higher tiers will help, too.
The level has nothing to do with it.
You might help yourself by replacing the $%§$ Starter wedge in your bag, and by using any custom ball if you wanna invest in the fun of the game. Balls wear&tear and get lost but they drop the meter speed and add to accuracy and such.