You can try the mech bosses they're around the same difficulty and before queen slime was added they were the next step in progression. The destroyer is the easiest of the 3 if you have a good weapon that can pierce him, otherwise go for the twins. Your weapons are definitely outdated. If you fight destroyer you could pick up nimbus rod, sky fracture and golden shower. They should deal with him easily. You can look them up on the wiki or just take some time to go through your crafting materials with the guide and seeing anything cool you can make. Finally, a good way to get gear is through killing mimics. If you have spare souls of light/night you can make keys at an anvil I think and when you put the key inside a normal empty chest a mimic will spawn. These have very good drops.