dont be a summon necro, coz i n every baal games, summon necs lag the game up and u lose exp from the game lagin, coz monsters come from no-where, second of all, dont go out there castin shit loads of bone walls or prisons coz they make the game laggy as well, only cast bone spirit or spear as ur attacks, poison is ok, but think of the poison resisits, so i suggest go for a bone necro, oh, and go for some curses as well, like life tap
just edited this, i dont really know the best necro gear, but try gettin arm of king leoric, wire nigma or wyrmhide, coa (if ur poor, only go for shako) homunuculos or wateva that shrunken head is, marrow walk for ur boots, frosties if u want mana increase, +25 maras, 2 sojs or bk's, and thats about all i suppose