In the early game, you want to poke with your W ONLY when you can stack manaflow band. Manaflow band and Presence of Mind should be able to keep your mana afloat to lane. Periodically send out a hawkshot to track the enemy jungler, keep an eye on objectives, or check brushes. With this build, you won't need to dedicate gold, time, and an item slot to stack a tear.

By now, you should have your manaflow band stacked fully, you want to secure vision on the map and around objectives with wards, using Hawkshot to scout the jungle first so you don't get killed. Position yourself so you don't get focused first, and play for picks with your ultimate. In teamfights, spam your W as much as you can so that you can proc your mythic item's ability.

In the late game, continue to spam all of your abilities, slowing enemies, getting vision, and getting picks. It is fine to use your ultimate liberally since you have so much ability haste from your runes and items. Your main focus should be applying slows, grievous wounds, slight burn damage, and armor shred on as many targets as possible. You can be a bit liberal with your positioning as well, since you will have a lot of health and some resistances with Demonic Embrace and Black Cleaver. You can act as an engage for your team by firing off your ultimate, or you can use your ultimate as a stun for key targets in teamfights.