Early Game Prioritize Melee Lifesteal & Spirit Strike. Buy in any order after. Move your mouse over the items for details! Mystic Reach is NOT mandatory and can be skipped for Mystic Vulnerability if you want more damage.
Mid Game Buy left to right. Upon unlocking your first Flex Slot, get Heroic Aura. If you don't have a flex slot yet, upgrade Headhunter and Titanic Mag first.