This isn't an in-depth guide. I am just posting what I know to work well for survival, starting with no wealth on hardcore.
Skill allocation:
-- 1 Skill point should go into every pre-requirement of the skills I mention.
Skeleton Mastery - 20
Raise Skeleton - 20
Raise Skeletal Mage - 20
Revive - 1
Clay Golem - 1
Golem Mastery - 1
Summon Resist - 1
Bone Armor - 1
Bone Wall - 20
Bone Prison - The remainder of your points go here.
Revives aren't worth the points you could spend to increase your bone armor's durability. One point is enough for even as few as +2 all skills to lift them out of the 'pointless' range. I admit that maxed revives are helpful, but they seem to go into cardiac arrest after 3 minutes and don't follow you as rigorously as your other summons. Unless you have enigma, the points that would be placed into revive are much well-spent elsewhere. Keep in mind this is an untwinked hardcore build...
Bone armor is pumped higher by the synergies than by maxing the skill itself. Bone Wall can be a useful skill; boxing yourself in with a nice town portal can be a nice break from the chaos. Also, level 10+ bone prison in hell can stop a PI in its tracks, giving your mages a chance to take it out. Prison has other uses as well; use your imagination.
Amplify Damage is the only useful curse you will personally take advantage of. Unless you plan on teaming up with melee characters often, and even sometimes in this case, this is the only curse you will need to put points into. To get to the other useful curses (that you won't directly benefit from; i.e. lifetap benefits your melee party members, but doesn't help your skeletons as much as amplify does) requires a ton of pre-req points that would be spent more wisely when used to pump your bone armor.
Items:
Pretty much whatever you can get ahold of...
At the time, I'm using Undead Crown unique helmet, a dusk shroud with four perfect Topaz in it, a rare wand with +2 to necromancer skills as well as +life, +energy, and some other useful mods. I also use a necromancer head which I got from Anya. A lot of skeleton bonuses on that : ). The Anya quest is very useful for the great class items (especially for Paladins and Necromancers) as well as (obviously) the resistance bonuses.
Any items you use should contribute to your Necromancer's tanking ability, even though you are supposed to be evading attacks from enemies. Sometimes your... we'll just call them special... skeletons won't be there in your time of need. Things such as faster hit recovery won't be needed as much as +life, +1-3 to bone armor, or even run/walk speed. Sander's boots are exceptionally useful for getting your *** out of harm's way.
With your skill points allocated as I listed, you will be able to survive fairly easily in hardcore indefinately. I've only ever died with this build one time, and that was due to a C/I after using a waypoint... x.x
Skill allocation:
-- 1 Skill point should go into every pre-requirement of the skills I mention.
Skeleton Mastery - 20
Raise Skeleton - 20
Raise Skeletal Mage - 20
Revive - 1
Clay Golem - 1
Golem Mastery - 1
Summon Resist - 1
Bone Armor - 1
Bone Wall - 20
Bone Prison - The remainder of your points go here.
Revives aren't worth the points you could spend to increase your bone armor's durability. One point is enough for even as few as +2 all skills to lift them out of the 'pointless' range. I admit that maxed revives are helpful, but they seem to go into cardiac arrest after 3 minutes and don't follow you as rigorously as your other summons. Unless you have enigma, the points that would be placed into revive are much well-spent elsewhere. Keep in mind this is an untwinked hardcore build...
Bone armor is pumped higher by the synergies than by maxing the skill itself. Bone Wall can be a useful skill; boxing yourself in with a nice town portal can be a nice break from the chaos. Also, level 10+ bone prison in hell can stop a PI in its tracks, giving your mages a chance to take it out. Prison has other uses as well; use your imagination.
Amplify Damage is the only useful curse you will personally take advantage of. Unless you plan on teaming up with melee characters often, and even sometimes in this case, this is the only curse you will need to put points into. To get to the other useful curses (that you won't directly benefit from; i.e. lifetap benefits your melee party members, but doesn't help your skeletons as much as amplify does) requires a ton of pre-req points that would be spent more wisely when used to pump your bone armor.
Items:
Pretty much whatever you can get ahold of...
At the time, I'm using Undead Crown unique helmet, a dusk shroud with four perfect Topaz in it, a rare wand with +2 to necromancer skills as well as +life, +energy, and some other useful mods. I also use a necromancer head which I got from Anya. A lot of skeleton bonuses on that : ). The Anya quest is very useful for the great class items (especially for Paladins and Necromancers) as well as (obviously) the resistance bonuses.
Any items you use should contribute to your Necromancer's tanking ability, even though you are supposed to be evading attacks from enemies. Sometimes your... we'll just call them special... skeletons won't be there in your time of need. Things such as faster hit recovery won't be needed as much as +life, +1-3 to bone armor, or even run/walk speed. Sander's boots are exceptionally useful for getting your *** out of harm's way.
With your skill points allocated as I listed, you will be able to survive fairly easily in hardcore indefinately. I've only ever died with this build one time, and that was due to a C/I after using a waypoint... x.x