You can lane with someone, or go mid solo, but either way you need the last hits. Stay ranged until you max out fervor, then swap to melee unless range is needed situationaly.
Once fervor is maxed out, and you have your morbid mask, start jungling. pop your ult as much as mana affords, and reap in the gold asap. Use this time to gank and assist where needed. as soon as you get mask of madness, rush roshan. blow it and your ult at the same time while in melee stance and you should have no real issues. pick up your aegis.
No start the real tormenting and trolling of the enemy team, blowing whirling axes at the start of your fight, as to build fervor asap, and keep them missing you.
If you are chasing someone, swap to ranged mode, use whirling axes, and swap back to melee mode quickly to catch them, mask of madness also helps here as well.
use your ult liberally, as it is low mana, and on a 20 sec cooldown, but if mana is an issue, save it for team fights.