Drow is pretty flexible.
I like helm of dominator, allows for easy ancients and jungling. Dominate a wolf/cat thing whenever you see one, have it follow you around for the bonus damage aura. Once you are more familliar with the game, you can have it stack ancients for you.
For boots, its either phase or treads. Most of the time its treads, but if you're going for agressive early game ganking/max frost arrows, I could see phasers.
After helm, I recommend manta style. Its great on drow because of her ult's massive agility bonus.
After manta its pretty much depends on what you need. Need more survivability against disables? Black King Bar. Need more survivability in general? Satanic. More damage? Daedalus. Fighting another carry with dodge? Grab a Monkey King Bar.
The one item I'm unsure about is butterfly. It costs more than daedalus/mkb but doesn't give as much damage, in exchange you gain 35% dodge, which sounds better than it really is considering dodge isn't always in effect (polymorphs disables it), and its only against physical. Adding onto that, one of its components is 3300 gold which is pretty hard to work up unless the other team isn't harassing you for awhile.
I recommend reading the guides on the first post for more information, click on the hero's portrait to see them.
edit: As far as builds go, you can afford to put 2-3 points into stats early for drow. Her aura doesn't give you that much earlier on, and also helps the ranged creeps push your lane (which is a bad thing). Traxex's last hitting is pretty hard early on, so stats help a lot. Also keep in mind with lifesteal builds that you can't use frost arrows and life steal at the same time, so whenever you need a snare just manually cast it.