I would say PvE-wise you can use the 50 staff atleast till 70. Further with masteries, fort etc.
Also get the 67/70 relic as thier proc gives you a nice boost to Mcrit aswell as Mcrit damage.
50 staff/67 relic and you can use that till 75 atleast! Longer if you fort it and put in ultimate growth and growth variant stones.
PvP wise I would say getting the 70 staff, 65 relic and 67/70 relic.
For armor I would reccomend making the 70 set, fersure. It's awesome.