FATE :
TBH in Fate there is no correct watch order, you can simply start with any of the fates, whether its the main timeline or the spinoffs. the things matters is what makes you get into the anime. you can just watch whichever fate you like. heavens feel for animation, 2006 for understanding, zero for story or UBW for overall quality. if i have to give an watch order then -
---> unlimited blade works
---> zero
---> heavens feel or 2006 fate
---> all the spinoffs/sidestories (apocrypha, fgo, encore, illya, etc)

MONOGATARI:
i think the order in which it got released is the best one, the one on this site. it gives you the best experience. But if you strictly wanna watch chronologically then -
---> Kizu
---> Neko
---> Bake
---> Nise
---> second season
---> Owari (this happens between the episodes of second season so dont be confused)
---> Tsuki
---> Kyomi (this has episodes from events spread between the entire timeline)
---> Owari second season
---> zoku owari
---> hana

HIBIKE! EUPHONIUM
i dont know if people find the watch order of sound euph confusing, but i did so imma give it to ya. if you havent this show, pls do, its kyo ani and in my top 20.
---> season 1
---> episode monaka
---> season 2
---> Liz and the blue bird
---> Brand new day
---> ensemble concert
---> season 3
---> season 1,2 and 3 specials and the photo seassion
---> skip the rest 2 movies, they are basically summaries

STEINS GATE
its not exactly confusing but you can enhance your experience by watching it this way. thats how i did it
---> original series till ep 22
---> episode 23b missing link
---> zero
---> original series ep 23 and 24
---> the OVAs

i cant only think of these for now, if you want watch order of some other animes, i can give it to ya. i havent watched haruhi and stuff so i havent included those, i know those are a bit confusing, i will post it once i watch it ig.