The Emerald Warden has very high natural damage output thanks to his abilities but very low health, so items should be geared towards survival. Early on, a Ring of the Teacher can give you much-needed mana regeneration and armor. You can either choose Ghost Marchers to boost his sub-par (290) movement speed, or Steam Boots on strength to boost HP and attack speed. You'll also want to pick up a Blood Chalice or Bottle early on, as the Emerald Warden chews through mana quickly with his spells. Later on, Frostburn is always a safe pick, as the slowing attack synergizes naturally with your long-ranged, kiting playstyle to pick off enemies and keep yourself out of harm's reach. If you make it past Frostburn, Wingbow, Assassin's Shroud, or Savage Mace can make you nearly untouchable while putting out massive damage.