For easy ability points (say, 4-8 per battle!) go to the basement of Bal Castle in World 2. Here you'll encounter Statues in groups of 2 (4 ability points) or 5 (8 ability points). However, you will most likely find yourself having difficulty with these stone warriors. Using a Soft potion will kill them instantly! Just keep stocking up on Soft potions and master all those classes that require hundreds of ability points!