This was my experience, too. A Skeleton Key To Finnegan's Wake by Joseph Campbell helped me understand the overall themes of the book, and hearing Joyce read it helped me appreciate the language and the rhythm of the words. I found it more approachable once I saw it as a story told in wild poetic dream sequence imagery.
The only thing I know about it is that the book is supposedly the inspiration for the naming of the quark. I feel as if this satisfies any obligation I have regarding it.
It's been sitting on my shelf for a few years now. I take it out and read a couple of pages each time and then put it back. Keep thinking I should buy a guide to reading this book but never got around to it.
Even a short summary of the Wake can suffice to get you started. You're never going to understand it all, and that's okay, but even a brief chat with a Wake fan can give you the basic clues of its structure and the HCE/ALP Shem/Shaun dualities. I think it's a mistake to spend time with guidebooks than with the text itself if you want to read it for pleasure as opposed to writing a thesis on it. At least, postpone the guides until after your first trip once around.
You might consider visiting Dublin on the week of June 16th and partake in the readings and pub crawls... though there are other Bloomsday commemoration events. That said, the only time I've stumbled across this was trying to find a seat in an Irish pub in the early '00s and being confused as to why it was that busy that night.
Listening to Joyce read it aloud: https://m.youtube.com/watch?v=M8kFqiv8Vww&pp=ygUcam95Y2UgcmV....
I had so much trouble trying to read him before understanding the intended pacing. It's more poetry than prose.