I have never heard the King's Indian described as "easy to learn."
Maybe easy to learn, but hard to master. 
QGD, orthodox or Slav could fall in that category IMO, as a easy to learn and easy to play.
I have never heard the King's Indian described as "easy to learn."
Maybe easy to learn, but hard to master. 
QGD, orthodox or Slav could fall in that category IMO, as a easy to learn and easy to play.
I haven't played these for years, but isn't it easy for white to transpose from one to the other? Isn't learning just one of these inadequate for repolying 1.d4 d5?
Well my rating can't compare to most of the people here, but as black you need a good defensive posture and you may not get the chance to take advantage of something that quickly.
Anyone that has played me know I prefer my Knights in the middle game, mainly because the pawn structure is normally built to limit the movement of Bishops and temporarily hender Knights at times.
At some point white will start an attack and most of the time that's when they are vulnerable if you have a good defensive position. And that's when you can strike.
(embarrassed look) yes I knew that, slip of the coordinates :)
I meant to say the Pirc, but in fact the Caro-Kann is probably a good beginner's opening too.
As for the King's Indian, it's easy to learn in the sense of being a single opening for black to learn instead of the myriad you need to study if you reply 1.... d5. But there are quite a few variations you need to study, sure.