The fastest way to get what you want is to rush to Eater of Worlds & a set of Demonite equipment.
I've found the fastest way to do that, starting from scratch, is to obtain the following
- At least two pieces of silver armor, or better
- A bow & arrows. Copper is good enough but better will make things faster.
- Ironskin potion. This is the key element - it's frankly overpowered.
- Regeneration potion. Not as strong as Ironskin but very easy to craft.
- A stack of Shuriken
Then you kill the Eye of Cthulu, which drops demonite ore. With demonite alone you can only make the axe, bow & sword.
What you really want is the Dryad, who sells purification powder. This lets you dig through ebonstone and smash shadow orbs. Smashing shadow orbs lets you fight the Eater of Worlds and obtain Shadow Scales, along with even more demonite. (Smashing three orbs is faster than farming for worm food.) Before you venture into the corruption chasms, be sure to obtain a hookshot. When you fight Eater of Worlds for the first few times, use an Ironskin potion. I find that grenades slay Eater very quickly, and they're reasonably accessible.
Summoning Eater a few times through orb busting will net you the highest defense armor short of Hellstone; a pickaxe that can mine every pre-hardmode block; a fair quality sword, axe, bow, and hammer; the musket & arms dealer; and some nifty trinkets.
A full set of Demonite gives enough base defense to farm Eye and Eater without buff potions, and pre-hardmode I am aware of no faster way to obtain coin than farming these bosses & selling their drops. You will also activate the goblin invasion, which you must defeat once for the tinker and mechanic.
In some worlds, the crimson replaces the corruption, which also replaces ebonstone with crimstone, demonite with crimtane, and the Eater of Worlds with Cthulu's Brain. None of these substitutions breaks the overall strategy.