Go for solo mid and try to stay in the lane with the Tangos and Wraith Band until you get the Power Treads. I usually go for the Power Treads straight, without buying the pieces separately, but if you feel like you might get ranked, buy the pieces off with Gloves of Haste first, then Boots of Speed and the Belt of Strength.
You should have your power treads at something like 5-8 minutes at level 7-9. After this get the Magic Wand, Another Wraith Band and some TPs and start roaming for Tier 1 towers, taking them all down.
Next, farm the Crystalys, then the Demon Edge and then the recipe for the Daedalus and you'll be a critical hit monster at level 14-16. Around this time roam the Tier 2 towers and take them all down. Then it's time to start farming the Butterfly or pushing the base, which ever feels better. The Desolator is a late game luxury item, which I rarely have time to farm.
Pros / Cons
Good harassing with long range shots. Great for pushing towers early and mid game. Reasonably good mid game ganking, less good late game ganking, unless you have an AoE stunning initiator or other carry to help take down the enemy heroes HPs before finishing them off with the long range sniping and Assassinates.
Risky early game with only Wraith Band and Tangos. Not very good late game. Could use a mana boosting item, like Arcane Boots or something in the late game to be able to spam Shrapnel and Assassinate.