Easy experience on "Generation 1":
After defeating the Jumbo Cock Boss in the Cave of Origin during Generation 1, go back down into the Boss room in the dungeon toencounter the Boss again during random battles. If your party is still kind of weak, then this can be a challenge because he can also spawn with as many as eight other monsters. The rewards as far as experience, gold, TP, and EP really stack up since you are able to win the battle faster. Save the game after each fight to avoid losing your levels, since this battle can go bad very quickly. Also, this is the only room you can find Mandrakes, which is also required for the Cave of Origins Title located at the Adventurer Hall, the requirement of which is to kill fifteen of each monster in the dungeon.