Question: Where is a good location to gain Ability Points in the second world?

Answer: The basement of Bal Castle has a monster called Statue or Objet d'Art depending on your version of the game. This monster can be killed in groups easily with the Blue Magic Level 5 Death.

Level 5 Death can be learned by Page 64 in the Ancient Library. Make sure that you learn this spell from the monster so that you can make use of an easy way to master nearly all of the jobs in the middle of the game.