Hey! So the first thing to note is that very few of the LNs are really connected to each other, and like half of them are adapted into anime so it depends on what you've seen already. But here's what I'll say. Fate/Requiem and Fate/Prototype Fragments of Sky Silver can be read anytime. Fate/Zero is up to discretion, but I recommend doing it after Stay Night. El-Melloi Case Files should be done after Zero and Adventures of El-Melloi should be done after Case Files. Apocrypha can be done at any time and Labyrinth and Lost Einherjar are both after it. Strange Fake I would recommend doing after Zero, Case Files, and Stay Night. Keep in mind that a lot of these aren't fully translated and only some of the ones that are have good translations. It should also be noted that many of these are in their own continuities or at least ones that are separate for each other, so my order is really based on how heavily they either canonically connect to other stories or lean on events of other stories. Really it's a safe bet to start with anime first and come back to these after, but up to you.

Thank you so much!

Oh yeah, forgot to ask, does it matter which series I start with between Kara no Kyoukai, Tsukihime, and Fate?