For starting out Drukhari, I would highly recommend starting out as kabal over coven, simply because monetary cost wise, coven is going to be significantly higher as wracks are twice as expensive as our other troops for reasons beyond me. Also if you can find the old Dark Eldar start collecting box, which came with an archon, raider, 10 kabalites and 3 reavers that's a pretty good discount on the core options you need for kabal, and you could always sell off the reavers if you don't want to have any wych cult units at all. There's also the kabalite skysplinter box you can sometimes find on ebay, nice discounted box that comes with 10 kabalites and a raider.
For a list, an archon, 2 x5 kabalites with a blaster each, a raider, a venom and a triple disintegrator cannon ravager puts you at about 460pts. I think that's a solid starter force, and when you build to 1000pts you can basically just double what you have to fill out a kabalite battalion, or you can go for adding on some coven forces.
The Night is Dark and Full of Terrors...