Ok here's what I recommend for before watching Blade Runner 2049:
Watch Blade Runner: The Final Cut (from 2007). Beware that there are other versions but they are worse. The original one that aired on the cinema was especially bad, since they changed the ending to make it "happy".
Listen to this episode of iddle weekend (they start discussing BRTFC @ 54:40).
There's actually more things you can watch before BR 2049; they created 3 free short movies as well. They "link" the events between the original one and the new one. Here they are: