You'll probably only be around level 60 with Ogden at the game's end; so you'll need to do a bit of grinding to hit level 99. The first thing you'll want to do is dismiss all of your party members except Ogden at the Inn located in Tundaria.
Once you have done that, have Ogden travel to the southwest end of the island and enter the cave down there. Once inside the cave, simply grind levels by fighting the clams. Once all clams are killed, exit the cave and then reenter. All clams will reappear for you to kill them again and keep repeating until you hit level 99 with Ogden.