I dont know about other items, but Umbrage and Signet of Twilight as Agility items are a nobrainer, thats for sure... Crit boost on those two 284 ilvl items is insanely good.
Other items should be Strength i guess...
Stalk arround the PvP ladder a bit, and inspect high rated Rets. That should give u a clue on what to go for.
I personaly think that you should get:
Penumbra Pendant
Apocalypse Advance
Both HC 284 ilvl...
Considering the armory u linked.
After that, if u get more coins, get Umbrage and Signet of Twilight HC.
Winding Sheets can be looted in a pug, but Gunship cloak HC is good enough on its own (i saw a lot of high rated Rets use it over Sheets), so there is no need to waste coins there.
The last item u could get is Bloodsurge or 277 WF 1h Wep for Healing. For Shield, farm 1800, should be ez enough...