Something properly thermostatted and controllable, is my main thing. It makes so much difference, and it’s one of those unfair things where it makes it easier for learners while experienced people can usually get good results with any old crap. You don’t have to spend a fortune though, I can’t find teh exact one I have online now (old model I guess) but it was about £50.
Hot air can be really useful too, I probbaly use the air gun on mine more than the iron. “rework station” is a good search term if you want that.