As you can see, on the top of the screen you can see the development. It will look something like this "12/50" or two, which shows you how close you are to completing that level. It can be done by merely "following the path" or by adventuring into dungeons and caverns and checking out new courses. All of it depends upon your options-- if you go off the path you will find incredible treasures, however you may also find difficult monsters! It will also contribute to your level progress, so make the options you attempt and desire to make it through for as long as possible!