One common theme is friendship. Their bond, whether it's growing stronger or falling apart, is often explored. For example, many fanfictions show how they supported each other in their early days as sorcerers.
One great fanfiction is 'The Bond Beyond'. It delves deep into the complex relationship between Gojo Satoru and Geto Suguru. It shows their early days at Jujutsu Tech, their training together, and how their ideologies start to diverge. The author does an excellent job of portraying their individual personalities and the strong connection they once had.
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.