Choose between two Nulls or two Bracers. I personally prefer to get Nulls cause in my conception, with the stun and a boot, you can escape of the most dangerous situations on the beginning. But if prefer surveillance, go for two (or maybe three) Bracers. Important: Be careful with your mana!! If you're going for killing instead of the supportive way, you must be patient in the beginning, cause your first item in most cases will be BKB (explained ahead), so your mana pool won't be so good, but enough to score some kills.
The items you'll start with depends of which enemies you're facing. Bottle, Magic Wand, Clarity Potions, Tangos, Circlets, Mantles, Wards, Chicken... they are all viable choices, but is up to you to decide this. If you're going mid, I highly recommend you to get Bottle and watch for rune control (explained later).