You get foundry weapons (suros,häkke,omolon) after rank one so that's cool. Plus at rank 2 you get a legendary quest which gives you a class specific weapon. At rank 3 you get an exotic quest. I think it was 100 kills with a certain weapon type while using a telemetry. After that, you dismantle specific weapons and you get the exotic! You only need 2 legendaries to finish the second step, exotics won't count.