What’s up with the pronunciation of 行き? When would I pronounce it as ゆき over いき?
The primary pronunciation is いき, especially in spoken language
ゆき is more literary (i.e. things like poetry and literature)
Edit to add: as far as where you may see the primary reading being ゆき in daily use, places of transportation would be examples, such as train stations, airports, bus stops, etc – 行き attached to a location would indicate where the train/plane/bus/etc is headed for (ex: 東京行き [とうきょうゆき] → “tokyo-bound”)
I’ve researched it a bit and it seems like ゆき is used when talking about trains (Such as “Bound for~”) and いき is used more to mean “Going” 
I’m not exactly sure though. That’s just what I’ve found online:
I’m pretty sure ゆき can also be a informal version of saying いき since it’s easier to say
https://www.reddit.com/r/LearnJapanese/comments/11efpn/difference_between_いく_行く_and_ゆく_行く/
This is great, I had someone ask me in a really thick Japanese accent if a train was heading to Brooklyn or not and this would have been really helpful!