I'll be on the broke diet
When people restrict themselves from something its called a diet. Like when people are overweight they have a diet which is restricting them from a lot of food.
Game is saying he’s restricting himself from being broke, he will never be broke.
Perhaps Game has join Joe Budden’s club NBA (Never Broke Again).
To help improve the meaning of these lyrics, visit "Switch Lanes" by Tyga (Ft. Game) Lyrics and leave a comment on the lyrics box