It is very simple, in such places as the Yensen Desert or the airship where you rescue the princess Ashe, you can just take your time in the maze-like passageways and wander around without leaving the area and the same type of monsters will spawn, heal after every battle and continue until you have chains going up to 300.

When you get back to town you will hae enough items to become very rich as well as attain levels, it is a good idea that wherever you find these points you use them to the fullest potential.