Toge Inumaki is important too. His special cursed speech ability makes him stand out. Also, the principal of the school, Masamichi Yaga, is likely to be important as he is in a position of authority and has an influence on Gojo and the other students. There could be other characters like the members of different clans that also play roles in the complex web of the story.
The memes in " Celebrating Years " referred to the memes that had some homonyms in the names of the characters in the play. For example, Fan Xian's name had a homonym of " making a nuisance," which meant that he was an annoying person. Fan Sizhe's name was a homonym for the famous brand " Versace ", implying that he was good at business. Fan Jian's name was a homonym for " cheap ", which matched his character. These jokes added some humor and interest to the characters in the play.
It's hard to pinpoint exactly where Gojo is at any given time in the manga. His whereabouts change as the story progresses and different scenarios unfold. It could be in a supernatural realm, a mission site, or interacting with other characters.