For archers, I know must do's are with the poison AoEs.
I would start empowering Mist at lvl 51, and start saving up points for Piercing at 67. The standard is max cooldown, but I recommend adding in attack power or sp (power for attracting aggro, maybe sp as they burn SP quite a bit e_e)
Aimed and Power Shot is a must too xD Max attack power/cooldown seems like a good choice.
>edit
Oh wait PvP archer LOL.
The above is mainly for PvE, since archers are amazing AoE solo'ers (and partiers in the right condition) xD Not sure what to recommend for PvP haha.
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