Best 1st Batman Omnibus

Hello everyone. I recently got into comics and more specifically Batman as he's one of my favourites. Instead of collecting single issues or one shots i decided to buy an omnibus but i don't really know which one is a good start for someone who has never bought one. Do mind i already have some stories like: Year one, The Dark Knight Returns, The Killing Joke, Arkham asylum, The Long Halloween and Dark Victory.