What do we know about their time in gangs? Presumably it was before they became recording artists, right? A lot of Death Row people (kurt kobane, suge knight, etc) claimed Tupac was with the bloods and he often talked about gang life in his lyrics - was Tupac's only real gang connection through Suge Knight?
thefroggfather did a pretty good job of summing it up, even using the interview I would have.
However, I would disagree with Suge being the only serious gang connection. IIRC, Pac was instrumental in creating a truce between Bloods and Crips. You don't get that with only having one serious gang connection, especially not when it's between two gangs with such history.
Also, I know you were asking specifically about Bloods and Crips, but I think*(edit) it would be worth mentioning that pretty much all of Pacs family were Black Panthers, who were considered a gang/terrorist organization. So, strictly speaking, he did come from gangs, just not crips and bloods.
1996 was not early in his career, either. 2pacalypse came out in 91*(edit) and was pretty much exclusively about politics and being black in America/growing up in poverty (look at trapped for an example). Pac died in 96.
Lastly, there is a pretty amazing Pac post on here. https://www.reddit.com/r/todayilearned/comments/1ko3gn/til_that_tupac_shakur_vehemently_denied_being_a/cbr3vxo