what spring kit do you have.
there is no absolute that says 'at this point you need a camber kit but at this point you don't'. It depends on a lot of factors.
here's the basics, 1.5" drop will put you on the edge of excessive camber. Its important you have less negative camber in the rear than in the front (helps with handling). Toe is the greatest cause of excessive tire wear, though. too much, in or out, will really kill your tires. camber is less of a concern there.