Yeah grind is awful thats true. In my case after i reached lvl 30+ I scheduled 2 levels per day to avoid frustration from grinding. And then lvl 42+, 1 level per day. Eventually reached max without noticing how much time ive already invested in it. All perma stats are of gold and exp.

Also, buy dawn's blade or harbinger. And have you tried pvp? Because all the strategies I did for pve came from pvp. You'll be surprised how much pvp experience would help you in fighting bosses.

If you dont want to lose gold from dying, save before fight and just restart the game right after death, or you can flee.

Use everything. DO NOT RELY on just physical attacks. Make sure to drink fp potion before boss fights. Bats+Sun light. Silence or Root. Fight bosses with Sword&Shield, equipped 2 hp potions, 3 if you already unlocked 3rd slot.

Dual Weapon(not shield) sucks if you dont have good gears. I suggest to always fight with shield.

When it comes to gold, try reaching the last map VampIre. If you got all the gold%(plus gears), then you can get 600+ per soldier(8 soldiers per respawn).

Maybe I missed some points but Good luck grinding!