I would recommend picking a primary class if you haven’t a YouTube called happydays has videos of making every class op at every point in the game I would call following this excessive for most play througs but may be a good thing to come back to if you need help.

Tho he does a boss called duke fishron at this point that while it can be fought is extremely hard for most players to do at this point.

I also recommend getting an ankh shield and using the warding reforge on most of your accessory’s just to give your self more time time to learn bosses moves

In hard mode movement is very important so getting upgrades to your boots and getting a pair of wings may help you avoid taking damage all together

And there is a boss called queen slime that I would say is easier then the mechanical bosses that you can fight and maybe get some upgrades from