I rec this fic over and over, because now and then there's an FFX who hasn't found it yet. Clarion by Justira, the story of Braska's pilgrimage, with emphasis on the summoner-aeon relationship.

Something to enjoy when you're done this playthrough. It's one of those "so good, my brain accepts it as canon" fanfics.

Owlmoose: agreed on the bond between Bahamut and Tidus, which is really quite interesting, since Bahamut's fayth has to travel a long way to reach dream Zanarkand and watch him. (Or maybe not far at all, if we accept my theory about dream and the farplane being practically adjacent in metaphysical space with some overlap, making it easy for Sin the death-aeon and unsent to cross.)