At some point I’ll post a fully fledged guide, but to get you started, this is what I’m doing (and has been very successful):
At level 2, choose Necromancer mastery, put 1 point mastery, 2 points in Raise Skeleton
Up to level to 6, put all points in Raise Skeletons, leaving just the single point in the mastery
At level 7, visit the Spirit Guide (back right corner of Devil’s Crossing), and remove all points from Raise Skeleton, place 15 points in Necromancer mastery and then the rest in Ravenous Earth
From here, all points go towards Ravenous Earth until maxed
Then 25 points in Necro Mastery, max Decay, max Spectral Binding, 5 in Spectral Wrath
Then put 10 in Occultist mastery, 1 in Curse of Frailty, max Vulnerability
15 in Occultist, max Blood of Dreeg, 32 in Occultist, max Aspect of the Guardian
40 points in Necro, 1 point in Foul Eruption, 1 in Blood Boil
50 points in Occultist, max Possession, max Doombolt
Then max Siphon Souls, max Blood Boil, 50 points in Necro
For devotions:
1 Eldritch Crossroads
Bat (bind Twin Fangs to Ravenous Earth)
Viper
Eel
Wendigo (bind Wendigo’s Mark to Curse of Frailty)
Spider
1 Order Crossroads
Crane
Rattosh, The Veil Warden (bind Will of Rattosh to Siphon Souls)
Oaklaine’s Lantern
Scales of Ulcama (bind Tip the Scales to Possession)
Hawk
*Remove Spider (go to Spirit Guide to remove those points)
Panther
Solemn Watcher
*Remove Crane
1 Primordial Crossroads
Obelisk of Menhir (skip the two on the middle right side)
The gear is outlined in JoV’s post in that thread (at end game), but you can get some of that before max level, and there are some lower level versions available at 35 and 65 in some cases.
Focus on the following stats on gear, in very roughly this order:
Vit Dmg, %Vit Dmg, %Vit Decay, OA, DA, +skills, Health, Energy/Health Regen, Resists, CDR, %Chaos Dmg, Reduced Stun Duration
For attributes, I put first 10 points in Physique, then 10 in Spirit, then keep going Physique until at least 50 points or so, can add the 10 in Cunning whenever, then rest in Physique.
Playstyle is pretty much just drop Ravenous Earth and let things explode. For tougher mobs, debuff with Curse of Frailty, then Ravenous Earth. Use Siphon Souls when surrounded for AoE damage/life steal. You’ll keep Spectral Binding and Possession (once you have it), toggled on at start of play. Keep Blood of Dreeg up (can cast every 15 seconds or so, or at most every 30). That’s pretty much it. At high levels, you can add in Doombolt on cooldown to nuke things. You can also use Mana Infusion (from the relic, from the Lost Elder quest in Act 2; lie and keep the amulet) for mana regen/extra damage for bosses.
As I said, at some point I’ll post a more detailed guide, but that should be more than enough to get started.