"Free like OJ" refers to OJ Simpson's acquittal in his highly publicized mid-90's trial for murder. He got off with no jail time, therefore Pac is referring to OJ as a free man
Trick:A broad term for describing women who are either teases, hoes, or one of the above pretending to be the other. Calling a woman a trick shows you are not impressed/convinced by their shit.
2pac says to tell his people he's a rida(he's down for watever) he's a outlaw. He says "nobody cries when we die, we outlawz let me ride" basically let him go in peace because life goes on
Bugsy Siegel was an American mobster from the 40s that went to Nevada and built a casino (The Flamingo). The casino was considered legal even though where the money to start it came from was questionable and was built with black market material