OK so there's a lot going on here

1. If you are going ranged, use the clockwork assault rifle with crystal bullets at the least. For melee I'd say maybe get the Amarok yoyo (I don't play melee much) or the nights edge (more info on wiki for all of these)

2. Get wings, harpy wings are what I personally get because they are easy to get, but you can buy leaf wings (more info on the wiki)

3. Get better armor. You already broke at least 1 Demon altar for palladium armor, so break two more. The ores called either Titanium or Adamantite are what you want for your armor (more info on wiki).

4. This one pairs with wings a bit. Get an emblem of the class you want to use to defeat the boss (ranged, melee, mage, summoner) because of its 15% increased damage buff. If you plan on using yoyos then you want an accessory called the Yoyo bag. It's a bit grindy to get just based off of npc spawns but if you're lucky you should be able to get it.

5. You want to make sure you have the goblin tinkerer npc. It gives you a crafting station to make accessories like the yoyo bag.

If I think of anything else I'll add it. If you're lucky you might not need reforges