Wizzie Gear Question

[Trihaal]

Hey guys!

15 wiz here, don't really know how the INT to mana works, so can someone please answer this question for me? What is the better item/combo to wield?

2HB Staff of the Observers
+5 WIS +5 INT +30 MANA
or
1HP Snake Fang & Stein of Moggok
+5 DEX +10 INT +10 HP


Or, is there a better one hand option (replace the snake fang) for me that i can get for less than 400pp?

Thank you in advance!