Probably not a good idea to play this game high if you don't understand it. You are meant to select a second class at lvl 5 and a third class at level 10.
There are so many builds that use shadowplay, there is no "best." There are a few "bests." It all depends on how you play.
Figure out whether you want to be melee, range, or caster shadowplay.
Then choose battlerage (melee), archery (range), or sorcery (caster).
The rest of the classes is entirely based on playstyle based on what you want to do. CC a lot, heal a little, play defensive, burst.
There are over 140 classes in this game, and 36 of them use shadowplay.
http://archeage.gamepedia.com/Classes