If you want to play as a warlock and level him up quickly so that you can make him shine at the special threshold levels, you should start with an undead warlock. Will of the Forsaken is invaluable for a block because it provides immunity to Charm, Fear, and Sleep effects and can also be used while already affected by Fear or Sleep effects. Also, Undead Warlocks will gain more Intellect than Orc Warlocks.
If you want to play for the Alliance you can have a Human or a Gnome Warlock and it could be a tough choice because humans have Perception which is probably the only stealth detection ability at level nineteen and Gnomes have Racial Engineering and Expanding Mind, so he gets a little more intellect. Although you don’t have to follow what I say because I know that every player has their own ways and preferences.
Level 19 Warlock Twink Gear:
o Head – You will want green tinted glasses with the 8 Stamina enchantment on them
o Neck – Thick Bronze Collar
o Shoulders – Talbar Mantle which is a quest item from Wailing Caverns
o Back – Sentinel Cloak with Defense Enchantment +70
o Chest: tree bark jacket with +100 health enchantment
o Bracers – Mindthrust Bracers with the +9 Stamina enchantment
o Hands – Magefist Gloves with the Spellpower enchantment on them
o Belt – Keller’s Girdle
o Pants: Darkweave breeches with mystic spell thread on them
o Feet – Sanguine Sandals with the Lesser Speed Charm o + Stamina Charm though most prefer the speed charm
o Ring1 – Seal of Sylvanas Ring2- Lavishly Jeweled Ring
o Weapon – Warlock Staff with the Intellect +22 enchantment
o Wand – Skycaller