First thing you need to do is learn to effectively orb-walk. I know of a Drow guide that explains perfect orb-walking, I'll post a link to that.
You must solo with it and play defensively until you hit level 7. Then, the world is your oyster, no really. Use Acane orb to harass the ¤¤¤¤ out of your enemy, whether you kill him or not is secondary, Keep him pinned down and make him visit his base more often.
I go for a Midas o matter what, since you need to keep that gold clock ticking with it. But, I'd say go for a treads (int/str), 3X Nulls, Mystic > Orb > Void = Hex, Shivas/Orchid and later a Assault Cuirass. That should be enough to destroy your opponents.
And, about the treads, I normally initiate with the Ultimate and then Orb my enemies to death. So what I do it right after I cast Eclipse I switch back to Str treads as 9/10 times your opponents will target you since you obviosly have the most DPS.