Agility, then more agility, then possible some agility. If the socket bonus is agility (and only agility) you could get away with a hybrid if you wanted to pad a secondary stat a bit. Yellow = (deadly) agility / crit. Blue = (Glinting) = agility / hit
Meta's are buggered right now thanks to the "more blue gems than red" on Chaotic (told this will be fixed next patch) so you might want to go with something like Fleet (mastery/run speed)
Well, its mostly been said, but you predominately focus on pure agility atm. Personally I have a couple orange hybrid gems with an agility bonus to get my meta active for the minor run speed, particualary in regards to raiding its worth sacrificing 20 agility for the run speed boost unless you have it on your boots which is ultimately more efficient because you only lose 10 agility. If you don't have the run speed on boots, do as I suggest....lots of people will argue against it but they are wrong.