This is the skillset I run with on hardcore.
The most important synergy here is between Fetish Sycophants, Firebats and Pierce the Veil. Firebats is without a doubt the best ability for spawning fetishes. With the Vampire Bats rune it doesn't cost any mana to channel, only when you start casting it. With Piranhas being the only other active ability used a lot (for the 15% increased damage), this allows me to use Pierce the Veil without running out of mana. Grave Injustice is possibly the best passive ability in the game, no matter what class, and should be used by every WD build unless you run without a single ability on a cooldown. Spirit Vessel is a necessity on hardcore, but can easily be replaced on softcore. Spirit Walk is another necessity on hardcore, but is an excellent ability even in softcore, because of the mobility, survivability and utility it provides. I use the Honored Guest rune for the extra mana those times I need it.
As for items, you want the same as almost every other class basically. Int and trifecta (AS, CC, CHD). Some specific items, if you want to run pet based builds (which is the best atm, expect a nerf some time soon), are
Mask of Jeram,
Tasker and Theo,
Starmetal Kukri, and the
4 set bonus of Zunimassa's Haunt.