I just manually summoned the Eye of Cthulhu, going into battle with copper armour, tungsten broadsword, gold bow, jester arrows and plenty of lesser healing potions. I came rather close to death but I managed to stay alive. However, the Eye took off when I had his health down to ~1700. I'm assuming this means you only have a few minutes to finish it off after a certain point. Is there any equipment I'm missing to help kill the Eye faster and to help my survivability? If it's relevant, my current life is 120.
There are no "requirements" as when you are ready. You can just be well prepared.
Things to know about the Eye of Cthulhu:
- Can only be fought at night, that means spawn him as soon as it's ~7:30 ingame.
- Nighttime lasts about 9 minutes.
- Cthulhu First Form does 15 damage and has 1400 life.
- Cthulhu Second Form does 23 damage and has 1400 life.
More info: http://terraria.gamepedia.com.
I find that the armor does not matter much, as long as you have at least iron armor.
The best weapon to fight it in my opinion is flaming arrows. When I fought it, it was using a gold bow with flaming arrows. The gold bow set up for high initial damage, and the flames damaged it over time, making its health go down more quickly.
If you're in a world with Crimson, some of the Crimson Hearts drop Crimson Rods. This is a very easy way to farm the Eye, just place the reaincloud above your head and keep dodging in the vicinity of the raincloud.
Don't try to go for it with meelee weapons. Shurikens work great here, or a minishark if you have the cash. And keep dodging if you have low level gear.
The Eye will only stay around at nighttime.
I currently farm the Eye by just staying put with a crimson cloud above me, and whacking it with a Vilethorn. You can get around 7 a night with that.
Eye of Cthulhu is a breeze if you try and get gear from the Dungeon, after killing Skeletron, or the Underworld, after getting the shadow key from the Dungeon. Alternatively, and if you have enough explosives since you can't mine the blocks, you could blow up enough corruption/crimson in your world (depending on which it has) to destroy Shadow Orbs or Crimson Hearts. Both of these drop fairly good gear if you are willing to spawn a boss every 3rd destroy. If you can't do any of these at the moment and are just setting your sights on the Eye of Cthulhu, I might recommend just exploring the underground and the caverns for golden chests and also simply mining. Gear you get from the chests will occupy your accessory slots and for your weapons you can pray you get something good from the rare drops enemies have, like a bone sword, or make weapons yourself. The best self-crafted gear you can get from mining before hardmode 'll be gold armor or platinum armor, depending on what spawns in your map.
As people are saying, you don't have any specific requirements for beating the Eye of Cthulhu or any of the pre-Hardmode Bosses for that matter, but gear makes it much easier on you.
I would recommend having silver armor, sword, and bow but it is not needed. I would recommend bringing potions and if possible a friend who has already beat him. All of these is not really a necessity but It will make the fight a lot easier. Make sure to wait outside in the corruption just before dark and start spamming the button to spawn the eye of Cthulhu so you can have all night but it probably wouldn't take all night to fight him. Full tungsten would probably make a 100% chance as long as you do enough damage.