Shoulders, Chest, and Pants: Generic, as much Strength, Vitality (or %life, or both), and All Resistance as you can afford. If you can, get Pickup Radius, Armor, and/or Magic Find. Sockets on the chest and pants are very good, almost required.
Amulet, Gloves, and Rings: Critical Hit Chance, Critical Hit Damage, and Strength. If you can, get Vitality and All Resistance as well. IAS will increase your tornado ticks, but isn't required. Hellfire Ring and Leoric's Signet if you're leveling.
Helm: Crit, Strength, Vitality, All Resistance, and socket. I prefer an Andariel's Visage myself, even though it lacks a few of these. Personal preference, like I said before, you don't really need IAS for this build.
Bracers: I love Lacuni's Prowlers for the +move speed, but could get any bracers with Critical Hit Chance and wear a Tyrael's Might chest instead.
Belt: Immortal King's Tribal Binding is likely the cheapest Mighty Belt you'll be able to find with the required stats. You need lifesteal, the higher the better, and the +maximum fury is always good. In addition, it can roll a mod that reduces the fury cost of Rend or increases the damage of Bash, which is always good.
Boots: I love Firewalkers because of the unique affix. The unique affix "Burns the ground you walk on", allows you to break through environmental breakables just by walking into them, saving you precious seconds every run. Try and get them with Strength, Vitality, and All Resistance.
Weapon: A Doom Hammer is ideal because of the way cooldown spells get their damage. Cooldown spells get the damage from your DPS multiplied by the unbuffed attacks per second of your weapon... but if the APS of your weapon is below 1, it becomes 1. So you get a little bit of a damage boost from using a Doom Hammer because it has a slightly higher damage range but a 0.9 attack speed. So if you had a Skorn and a Doom Hammer with the exact same stats, and the exact same listed average DPS, the Doom Hammer would do a bit more damage on cooldown spells.
Unfortunately, finding a Doom Hammer with good stats is difficult. If you can't find one, a Skorn will work. High critical hit damage, Strength, and a socket are required, with Lifesteal being perfectly ideal but unnecessary.