MG genie for both PK and 1v1 :
100MG, 30DEX, rest VIT. Reason why you want 30 dex is to extend Extreme Poison's and Fortify's time with 1 sec, it's pretty much the difference between killing and getting killed.
Skills:
Will Surge
Extreme Poison
Holy Path
AD
Expel
Belief
Spark(it still boosts the damage a lot with 30 dex, 1 crit in a 2 fire skills combo is enough to hiero, in my case anyway)
Fortify
Dex genie is of no use to MG's in mass PK, first because nova can't be countered without using AD (which is a suicidal move if you use a low regen rate genie). Also 1v1 wise, dex genie against a good sin doesn't help at all, freeze and silence's time is enough to kill a MG. Only class that it could help against is WR, not against a good 1 though, that knows how to get through it. Overall, the mag genie I described above, if you're just a spark relying wiz that can't kill anything unless you hit 40k's a blow, then I suggest using dex genie for a kill, followed by imminent death.