I posted some information on Erudite Necromancer faction
here. In a nutshell, the "true evil" cities (Neriak, Grobb, Oggok) aren't very welcoming, and you'll be KOS in at least parts of those cities. On the other hand, you can visit some good cities that the other SKs can't, but that's of limited use.
One thing I haven't looked at is faction in Firiona Vie. I expect to be KOS, but I wonder if it's easier to fix as an Erudite than, say, a Dark Elf or Troll.
Oh, one other thing: there are a few SK/Necro spells that are only available from the SK guilds in Paineel, Grobb, and Oggok. As an Erudite, my only option is to buy them from Paineel. Not a big deal, but you'll want to pick them up ahead of time unless you want to make a cross-country trip for one spell.