Dirge is a perfect hero to start with. With Soul Rip he can be also be a support and with his ultimate and Tombstone plus his ability to steal strength, in teamfights he becomes very useful and game braking.
Bottom or top are fine, don't try to solo a lane. After all he's a tank/support that much like others heroes.
Great teammates for Dirge are ones that can create creeps for his healing ability or slow/stuns for bunch of zombies to be spawn, and more zombies are around, more damage for Soul Rip. Some examples are:
Coming soon. (WIP)