Chilean here, we have two classics:

1. Completo (as in “complete”, also known as Dinámico for “dynamic”): Diced tomato, sauerkraut, mashed avocado, chilean american sauce (finely chopped pickled white onions, carrots and pickles) and mayo.
2. Italiano (“italian”): Diced tomato, mashed avocado and mayo.

I’d normally go for the latter and save the former for special occasions.

I’m a simple person: Mustard, ketchup, and a decently made sausage. Maybe some onions.