Find the Monster Arena owner. Buy a weapon from him. Go and fight lots of Anacondours and steal 60 Petrify Grenades from them. Customize the weapon with Stonestrike. Capture all the monsters that you need in the Calm Lands. Talk to the Monster Arena owner. He will give you a chest with Nirvana, Yuna's legendary weapon. You cannot open it without the Celestial Mirror. Talk to the man. He will give you 60 Farplane Winds. Customize your weapon with these to get Deathstrike. Now almost any monster can be captured in one move.