As far as controller goes, I use the new Xbox Series X controller (specifically the new Shock Blue colour, because I couldn't resist the new look). The Elite 2 is a better option if it's in your budget....I tend to abuse my controllers too much, though - after going through 2 Elites in a short period of time (one of them being replaced by the other under warranty), I couldn't justify buying another. Most top lists will recommend the Elite, followed by either after market versions of the Elite or the regular Xbox controller.
In relation to headset, are you leaning toward wired or wireless? The HyperX Cloud 2 is a great headset that doesn't break the bank - and there are wired and wireless models to choose from.
I can't really comment on keyboard as I haven't done enough research into options.