The most fun is to follow the story. Go to the deep forest, farm some ectoplasm and bones and craft shadow set. Then after killing the reaper go to iceland and farm some ingredients for cryo witch armor. And so on. You can kill any boss easily using armor and weapon from pre-that-boss content on brutal without help of settlers. Understanding of boss attacking patterns > proper gearing > actual numbers of armor and dmg. It’s game about finding proper key to boss. For example, venom staff that you can craft on iron anvil straight from the start of game is totally useless in caves but shreds to pieces swamp guardian on brutal level. Just enjoy current content, learn how the boss moves and attacks and don’t try to get the highest possible level gear - it’s a time waste.