So Disrespectful

Before I Self Destruct 50 Cent
50 is refering to the Snoop Dogg song Murder Was the Case in which Snoop says "Murder was the case that they gave me" implying 50 is threatening to kill.
The IRS taxes people progressively higher depending on the amount of taxable income they report for a given year. These levels are called brackets. 50 is saying that he makes so much money, most people will never be taxed as highly as him.
50 Cent is implying that former G-Unt rapper, Game (BKA The Game), will never be equal to him, on any level.
Jay= Rapper, Jay-Z. He is trying to get a response from Jay-Z in response to recent mentions of the rapper, but explains that Jay-Z is too popular to respond to someone as lowly as 50 Cent.