Read Fulgrim. It is p good. Honestly its the last book that the Emperors Children arent downright comical and Im at book 33.
So heres the thing about what you linked there, a LOT of those books marked books are actually novellas and included in compilations.
So in order to read according to that chart, you would literally have to find the compilation the novella is contained in and read just that part. The one major exception is the Garro stuff who, after the flight of the eisenstein you may want to stick with a bit because you may find yourself attached to Nathaniel Garro which is fine but it will spoil things for you.
I am reading in the order found here https://en.wikipedia...e_Horus_Heresy_(novels)
Like I said Im 33 in with some with a few side audio dramas along the way. If you were going to shoot off in a different direction you can because the way it all works a lot of things are revisited throughout the course of the books so some skipping around is ok.
Honestly though, I think you kind of NEED Fulgrim, Descent of Angels and Legion because it really sets up 3 major legions that you will be hearing a good bit about and some of the nuances associated with them. I could go on about this but I wont unless you want me too.
Battle of the Abyss is good I thought though somewhat skippable/read later unless you know absolutely nothing about the word bearers and Ultramar.
Mechanicum you can skip unless you you want to get into the nitty gritty of Mars in the heresy.
Tales of heresy is the first compilation and while some stories are good others are meh so you can pick and choose when you get to these really.
Fallen Angels is another Dark Angels book and aside from the whole setup of The Fallen and one other neat plot bit its kind of skippable if you really dont care/dont like the DA and all their SPOOKY SECRET SPACE KNIGHT bullshit.
A Thousand Sons is a fucking must. Its great and its tragic and its just fucking amazing. Magnus did nothing wrong.
Nemesis is meh and totally skippabole unless you care about assasins.
The First Heretic aka Lorgar is actually a p nice guy. I thought it was good and it gives you a good insight to as of who they are as a legion. Also motherfucking Argel Tal.
Prospero burns is basically A Thousand Sons from the Space Wolves perspective with all the other wolf bullshit. If you like the Space Wolves you should read this because it is one of the few times you will get to read about them as a whole. I almost spoiled something but I deleted it. Again if you are a space yiff you need to read this.
Thats 12 out from where you are. Ive read about 90% of what is in your chart but in the order I linked above and nothing really sticks out to me as oh man i wish i would have read that here rather than there.
God speed and DEATH TO THE FALSE EMPEROR.