When to start dlc...

I saw somewhere that when you finish main game, bosses become stronger...so as i understand dlc bosses are available immediately? Im level 90 and i wanna be "a good player" that means i dont wanna use summons throwables in bosses wanna parry as much as i can is starting dlc before last boss considered "a good" player. I dont wanna give off negative vibes i just wanna be "a skilled player " whatever that means( even though im not so much haha)