Potions
Ironskin Potion
Regeneration Potion
Burger

Ironskin Potions are easy to get, you just need Daybloom, a Water Bottle, and 1 Iron/Lead Ore, to craft potions, all you need to do is place down a bottle on top of a work bench, and then you can craft potions. Regeneration potions use the same recipe as ironskin potions, but instead of Iron/Lead ore, you use a normal Mushroom. Burgers are harder to get, they are new to 1.4, and because of that they are not very well known, but you just need to farm eaters of souls in the corruption biome, and they will sometimes drop burgers, which are similar to bacon because they increase all of your stats (Damage, Armor), but unlike bacon, Burgers don't actually give you more life regeneration.

Weapons
Minishark
Quad Barrel Shotgun

these have already been talked about in the NPCs Section

Armor
The armor you will need is a full set of Gold/Platinum Armor, the Hermes Boots, and the Blizzard in a bottle accessories.

This is arguably the hardest hing to get in this whole guide, considering everything else you can get is inside your base, and so is this. To get large sums of Gold/Platinum, all you will need to do is set up a fishing area in your base, grab a Reinforced Fishing Pole/Sitting Duck's Fishing Pole, some bait, a few sonar and crate potions, and you are set to fish up some crates, the prehardmode Crates are the Wooden Crate, Iron Crate, and the Gold Crate, but you can get different crates in different biomes. The Hermes boots can be found in chests underground and increase your speed after running for a bit, but these can be replaced by the Dune Rider Boots, Sailfish Boots, or the Spectral boots, if you have those. the Blizzard in a Bottle can be replaced by the sandstorm in a bottle or the Spectral Boots, they can be found in underground ice biome chests.

Extras
These are Extra Items that you could use in the Eye of Cthulhu fight if you have them or are doing a class specific playthrough

Melee:
Star Fury, Enchanted Sword, Ice Blade
These are the only 3 Projectile shooting blades in Prehardmode

Star Fury Obtaining: The Star Fury is found in sky chests that you find on Floating Islands.

Enchanted Sword obtaining: The enchanted sword has a 90% Chance of Dropping from Enchantde Sword Shrines, the way you can tell the Enchanted sword will be in it is if there is a Blue Sword instead of a Gray Sword in the Shrine. Enchanted Sword Shrines can be found around the entire underground, but if you are looking for an easier way, you can find the sword shrines near the surface indicated by tiny one block gaps.

Ice Blade obtaining: You can find the Ice Blade in Underground Ice Biome chests

Magic:
Wand of Sparking, Vilethorn/Crimson Rod
These are the only 3 Early Game Magic Weapons

Wand of Sparking Obtaining: the Wand of sparking can be found in chests around the world, except for ice chests and jungle chests

Vilethorn/Crimson Rod Obtaining: The Vilethorn/Crimson Rod can be obtained by destroying Shadow Orbs/Crimson Hearts

Summoning (Note, this requires the Zoologist NPC)
Finch Staff, Leather Whip, Snapthorn
These are the 3 Summoning items easily obtainable in the early game

Finch Staff Obtaining: The Finch staff is found in chests in living wood trees

Leather whip Obtaining: Bought from Zoologist for 15 gold after filling in 80 entries in the bestiary, or after 80 different enemies are killed

Accessories:
Band of Regeneration: found in chests around the world
Cloud in a Bottle: Found in chests around the world

NPCs
The NPCs you will need are the:
Arms Dealer
Nurse

to start this part, you should put the Arms Dealer and Nurse in nearby houses in the desert, this will make the arms Dealer's prices as low as possible, to get the nurse, you need to increase your life with a life crystal, to get the arms dealer, you need to obtain a gun, the easiest way of doing this is going to the Corruption/Crimson and breaking Shadow Orbs/Crimson Hearts until you get the Musket/Undertaker.

What you will need from the NPCs
Quad Barrel Shotgun
Silver/tungsten Bullets
Minishark

these items will cost a lot, my reccomendation to getting these is to farm King Slime, though his normal drops don't sell for much, his expert drop, often considered useless, actually sells for 3+ Gold coins, and the master drops sell for a lot, all the master mode pets sell for at least 5 gold. For the Quad Barrel shotgun, you will need to die 5 times (it doesn't matter how, but I would recommend fall damage) and pick up the gravestones, then place them in your desert biome to create a Graveyard Biome, a new feaature added in 1.4, then you can go to the Arms Dealer and buy the Quad Barrel Shotgun, in total you will need about 50 gold for these weapons. But guns of course, require bullets to use, the silver bullets are the best ones you can get at this point in the game. to get them it needs to be a blood moon, then go to the arms dealer and buy (at most) 1998 (2 Stacks of 999) silver bullets.

Your arena should look similar to this (Note, this is my main Hardmode Arena, meaning it is meant to be used with wings, so different scaling was used)


It should have:
3 100 block long platforms, spaced 7 blocks (Y/Verticle) apart
Multiple Campfires spread 50 blocks (X/Horizontle) and 7 blocks (Y/Vericle) apart
Chests for loot (Optional)
Clock for time (Optional)

Strategy
The strategy for this arena is to stay as far away from the Eye of Cthulhu as possible while dealing lots of damage, when the Eye of Cthulhu is above the player, keep on running from it while using your Minishark to deal damage (at a Roughly 45 degree angle, or diagonally), but when it dashes, run from it while using your Quad Barrel Shotgun to be allowed to dodge more, when you run out of space on a platform, jump up to/ go down to the next one and change direction