If you are interested in getting to know about gangsta rap and some of its famous rappers in the mid-nineties, this is your movie.
Although it's from a Notorious B.I.G perspective but it also shows in a relatively unbiased way how the East Coast-West Coast rap rivalry and war started.
It's basically about the life of Biggie Smalls (the Notorious B.I.G.).

If you want to go a bit further, I recommend a 2002 documentary called 'Biggie and Tupac' and it tries to reveal what happened in 1996 and 1997 that lead to the killings of both Notorious B.I.G. and Tupac.