If you’re asking for a reading order, I can give a little bit of input when it comes to Revelation Space, but I haven’t read much outside of that universe.
The standard RS reading order goes Revelation Space -> Chasm City -> Redemption Ark -> Absolution Gap. Chasm City is a mostly standalone story that’s chronologically a prequel to RS, but it seems to expect a prior understanding of the RS universe, so you’ve got to have read RS first. It also establishes some ideas that are used in the later novels, so the best time to read it is after Revelation Space, but prior to Redemption Ark. I accidently skipped Chasm City, and there were a couple of moments in Redemption Ark where I got the idea that I'd missed something.
Redemption Ark, and Absolution Gap, are both of a lower quality than Revelation Space, I have to admit, but I didn’t regret reading them. The very end of the story (the end of Absolution Gap) is actually kind of mind fucking, and I enjoyed it a lot. The world building also stays up to par throughout all four novels, so in my opinion, it’s worth it just for that. The Conjoiners are a fascinating little faction, and you’d know next to nothing about them without reading the sequels.
The Prefect, and Elysium Fire, are both set about a hundred years prior to Revelation Space. They're entirely detached stories, and are purely optional. Personally, I found The Prefect mildly enticing, but the protagonist clearly isn't a very interesting character, as his sequel is the only RS novel I haven't read. Read these only if you've exhausted all other content.
That’s it for the novels. As for the short stories, they're quick, and easy reads, so I'd recommend reading them if you manage to finish the main RS sequence, and still want more. Of note are Glacial, and Diamond Dogs. Both have interesting concepts that I think are genuinely worth reading (if you enjoy RS, that is). There's also The Great Wall of Mars, which provides backstory on one of the characters from the RS sequels. I imagine the short stories are highly personal, though, so I'd recommend just buying the Galactic North collection, and reading them front to back. For example, I personally enjoyed Weather I want to teach Weather the ways of baseline human love, and by that, I mean sex but I wouldn’t recommend it to others.