I've just defeated Yunalesca and now i'm on the airship before the fight with Sin but it heard that it's better to do some sidequests before flying towards Sin as the battles with Seymour Omnis and Braska's Final Aeon are difficult but don't understand which sidequests should i do, i've completed the Cavern of the Stolen Fayth sidequest early in the game(though i didn't obtain Yojimbo because i didn't have enough gil) what should i do now?