I have done all sorts of characters but never a poison nova necro.

can someone point me to the best/newest guide or just recommend some stuff for me?

currently basic setup
hoto
P homun
arach
trang gloves
2-20marrows
shako
maras

have a dweb not the best but like -48 and 2 skill i believe.

no idea what to use. merc has eth gaze not andys since i know that can be a problem

You will want Death's web over hoto easily.

if a monster has 75 psn res and you do 1k, you do 250.
if a monster has 27 psn res and you do 1k, you do 730.

That's almost triple damages just like amplify damage

yea i figured i would want it. i just did the hoto for while i was lvling.

any other other tips? i know lower resist and nova but any advice on the rest of gear or how i should split up skills?

Depends how you want to go about it.
What areas are you hoping to run? Or just general mf?

CE is great to max but it'll make you turn into less of a poison mancer as once stuff dies you spam CE.

yea i use ce on the summoner obviously. i can make great summoners. I was mostly thinking just general mf but I had heard they were great for cows

Cows is just nova/LR or amp/CE honestly lol. Maybe pump iron golem/mastery for more survivability.

Psn necro is pretty simple. Just hit breakpoints and it dominates certain areas.