Summon necros can have alot of variety in how you build, but heres the basic build i do (i love playing around iwth a summon necro once in a while)
Raise Skeleton - max
Skeleton Mastery - max
revive - max
clay golem - max
golem mastery - max
Corpse explosion - 1-max (depends on if i want to or not)
amp damage - 1 (more if you dont have much + gear or dont plan to have much)
from there i just play around with what i think is fun, normally into more masteries, or maxing out a golem/mages. Granted people like to have bone spirit/bone prison in alot of builds, i like going full summon, just ads to some amusement having 50+ minions running around.