Well, one method is to check out fanfic review blogs or websites. Some bloggers dedicated to JJK will review and rank fanfics. Also, ask other JJK fans directly. You can go to anime or manga conventions where there are likely to be JJK fans. They might be able to point you to some amazing fanfics they've read. Additionally, explore the related tags on fanfic platforms. Sometimes, the less popular but really good fanfics can be found this way.
I'd recommend beginning at the beginning, so Volume 1. That way, you get the full story as the author intended without missing any crucial details or build-up.
I'd suggest beginning with the first chapter. It sets the foundation and introduces the main characters and the initial plot. From there, you'll be able to follow the story's progression smoothly. Also, check out some online manga platforms that have clear starting points and good reading interfaces.
'Sword Art Online' can be considered among the best. It combines elements of virtual reality, adventure, and romance. The concept of being trapped in a virtual game world and having to fight for your life is very appealing. It has a large cast of characters, each with their own story arcs, and the visual descriptions in the novel make it easy to imagine the virtual landscapes.
Which domestic animation was the best was a very subjective question because everyone had different preferences for animation. However, I can recommend you some well-received domestic animation works, including: Return of the Great Sage, Big Fish and Begonia, Rise of the Great Qin Empire, Return of the Great Sage in Journey to the West, Full-time Master, Nezha's Demon Child, etc. These works were not only successful at the box office and reputation, but also had high artistic value and cultural significance. I hope you can find your favorite animation works.
I'm not sure about legal places to read it for free with good translations. It's best to support the creators by buying or subscribing through official channels.