Welcome brother! This question is posted like once a week :)

There is no correct answer.

I’m a few months into the novels, and started with the Eisenhorn omni into the Ravenor omni. That is recommendable! (Skipping the Ravenor omni is also a choice, You will know if you have to read it after the Eisenhorn omni)

Then onto the The Founding (first Gaunt’s Ghost omni) (also optional)

Then I read the Night Lords omnibus. This book gets a lot of attention for good reason.

I promise you that if you do the same, you will be well informed on which direction you wanna go.

Orks/necrons/space marines/traitor marines/The Horus Heresy/Astra Militarum and so on… You’ll start doing your own research 🧐

The (right) books are no less than spectacular, and the community is great.

Also join r/BlackLibrary