Im farrrr from an expert; but it really depends on what your looking for and the kinda mood you want to express through your musical listening ^^ (I suppose that's true with most music, but its really really true for orchestral music)
If I'm in a dark brooding mood or Iv experienced something quite emotionally intense; then Bach (particularly the Bach played on an organ is amazing) ~ Bach has a way of almost mathematically balancing on the edge of chaos and perfection; its dark but its also really fascinating and in some ways quite reassuring for me. I'd recommend
The Art of the Fugue Orr if you're a vampire, than
this one (Toccata in D Minor)
Wagner can also be super; but Id put his music more in the zone of high fantasy ~ a lot of movie music and lord of the ringy type vibes are inspired by Wagner. A good one here is
Tristan und Isolde (The conductor on this video is super fun to watch) though in general I don't find myself listening to Wagner very often.
Orr if you in more of a Victorian high drama mood and you want to imagine you're in a Howls Moving Castle world, or you're on your way to a ball on a steam ship then
Brahms is ideal! He was quite a bit later than the others and I think he struggled to try and live up to the expectations of older composers; I appreciate that
There's also a whole world of modern classical composing that I have encountered and been really impressed by, but I don't know any names off the top of my head!