There is always the option to hide 2 squads of 10 kabalites in cover with a dark lance, run 6 incubi and Drazhar in the raider, and the Archon in Venom with undersized 4 incubi. Since Incubi without transports isn't playable IMO, they have the priority.
However, i would strongly advice you to consider transports as your future purchases (no rush, eh, playtest your army as much as you need first). Dark Eldars really need those.
Edit : my bad, you can't have an undersized unit if you have another one. So you could make something like 5 incubi in the venom, and Archon, Drazzhar and 5 incubi in the raider ?