Also depending on how long you have been playing and how much money you have you can almost create "celestial copies" that is weapons with similar abilities to the celestial weapons triple overdrive and break damage limit are essential in the final battles. Not triple overdrive as much as BDL but they are very helpful. Although creating your own perfect weapon with Probably BDL, Triple Overdrive, and then 2 extra abilities depending on the character (i.e. one mp cost for lulu and yuna etc.) this can be a very long and drawn out process.

As Xanatos stated you can always just grind and take an extra path or two on the sphere grid or get the celestial weapons, or make your own awesome weapons.
But this is very time consuming and in the end when you fight sin and braska's final aeon its very boring considering a summons overdrive when you have activated the celestial weapons can BDL and depending on how hard you grind almost always will anima, bahamut and shiva do 99,999. IMO that makes it kinda boring.