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 Apotheosis of the Heavens was a novel about the infinite heavens. It told the story of the protagonist rising from the insignificant, conquering the heavens and finally reaching the supreme world, fusing 3000 Great Dao into one to create the supreme Great Dao. This novel was super good, but the specific plot and details needed to be read in full to understand. The search results did not provide any other information about the Gods.