Like mark989us said, it's relatively cheap and quite easy to build one.
Since Universal Law set provides tons of nrg/mana, you can start to level with OoA if you have the sets and some Shrines.
It's bit slow at the beginning, but it will get much better and better.
(I'm still learning this game. So keep in mind that my suggestions are not 100% correct
)
I think
Witchmoon
Witchmoon
Amulet
Required Level: 100
Item Level: 100
1% Chance to cast level 17 Mana Sweep on Death Blow
+(1 to 3) to All Skills
+(10 to 20) Spell Focus
+(10 to 20)% to Spell Damage
Maximum Mana +(30 to 40)%
is BIS.
And rest of gears are just Spiritual crafted gear (or Eerie maybe).
Sash, Boots - focus on High Mana/Mana regen/ Energy
Circlet - *All skill*/ High Mana/Mana regen/ Energy
+ 2x
Empyrean Band
Empyrean Band
Ring
Required Level: 40
Item Level: 40
1% Chance to cast level 18 Singularity on Kill
(3 to 5)% to All Attributes
Maximum Life +3%
Maximum Mana +10%
(5 to 15)% Gold Find
or
Empyrean Glory
Empyrean Glory
Ring
Required Level: 50
Item Level: 120
1% Chance to cast level 40 Singularity on Kill
(6 to 10)% to All Attributes
Maximum Life +5%
Maximum Mana +15%
15% Gold Find
And I've been using random Crafted Assassin shield with Rune of Mana oskill (weapon swap) recently.
It's bit clunky/risky to use but it helps quite a lot for me.
So far, I'm sitting at 46k mana and 20k OoA dmg with shitty gear.
I can clear Dunc in 4 min with around 300mf now.
Teganze takes around 9min iirc. And even Fauz/Bremm is really easy/fast to run.