PvP power gems are pretty cheap on my server it seems the best way to go but im not quite sure if there is a pvp power cap and you should start going int at some point, if your having problems queing into melee cleaves etc etc then gem resil. Enchants are pretty self explanatory there isn't very many options. Reforging is a bit tricky because master/crit seem to be personal preference right now I personally go crit over mastery bc it also affects of heals.
Thanks everyone for their reply. I guess as far as offset pieces go, its crit or mastery depending on preference. If your playing 2v2 double dps with a mage, what do you think would be preferable? Look forward to any thoughts.