Yo, I keep running out of mana with my vengeance Pom. It goes away sooo quickly! 
The gear I use in PvE is bits and pieces of everything. Think it could be compared with khitai epic/blue. In PvP i run full PvP T1 but the problem is just the same… Hell i even spent 5 points in Ether Discharge, doesnt solve my problem… Yes, I eat tons of pots!
Any suggestions?
Just go full gen tree you’ll be fine
Not sure if you only want advices for PvP but for PvE the easiest way to not run out of mana is getting the Silver Twilight blessing. With the 6% mana leech you can easily skip most mana restoring feats and spec more DPS to leech even more. My PoM had mana issues before too but once I got the blessing I often can completely skip using mana potions if I get lucky with Holy Accession.
But obviously, in PvP that doesn’t work because of the debuff it gives.
Thanks for reply. Where can Silver Twilight blessing be obtained?
Chaos gems and T6 weapons + necklace. You need at least 2 items with the buff so the easiest way to get it is obtaining 2 chaos rings (or RF rings if you want) and 2 gems to put in that have the buff.
Gems with blessing buffs and rings start to drop at the second boss fight in the dungeon.
That is great news! These rings is really good for PVP aswell! 
The Constitution / Protection rings are good but the other ones got negative PvP damage on them, though I don’t really know how much that matters in PvP since the other values are still so insanely high.
Right, so i will need to gather all four rings! Damnit! 
What spec are you using?
The -PvP damage doesn’t cancel out the absurd damage they give. Fully slotted they’re waaaaaay better than the PvP rings.
Also even with top tier gear VENG is a massive mana sink. Its not like you can just spam nonstop and never run out no matter full aa’s and rings. Veng requires more resource management and rotation control than divinity for sure