Blood Magic: 16 (12+3+1)
Soul Reaping: 13 (12+1)
Blood Magic: Offering of Blood (elite) or Well of Power, Shadow Strike, Vampiric Gaze, Life Syhpon, Strip Enchantment, Demonic Flesh, Dark Pact or Well of Blood (if you choose Offering of Blood)
Other: Ressurection Signet
Weapon and Armor:
You can take Scar Patterns or normal Armor. In this build you shouln't have bigger problems with energy.
For weapon use Staff with bonus to energy and bonus to HP. Staff should have "Improve skill cast/recharge using Blood Magic".
How to play:
It is just damage type build. You can do with this build about 210 damage in 4-5 seconds plus damage that Life Siphon do. Remember that Shadow Strike need to be cast only if foe has more then 50% of his life.
When you choose Offering of Blood then cast it always. Right after recharge.
When someone dies and you got Well of Blood, cast it immediately. Necromancer that stands in Well that gives him +6 life regeneration and +3 from Siphon is very hard to kill.
With Well of Power you may have problems with energy but don't be afraid. Soul Reaping is very helpful attribute.
Use Strip always when you're attacking a Monk or Warrior. They probably have some buffs so it will be easier to kill without those buffs. On other professions use Strip only to heal yourself - in critical situations try to find Elementalist because there's a big chance that they will have Enchantment.
Demonic Flesh is one of best Enchantment in game! Try to have it always. Cast it even if you have small amount of life!