From what I can remember I got to level 99 on my first play-through just killing various creatures in the DS version. All I did a grind on the Nu in 600 AD for my techs while taking my time in certain areas killing other creatures. Getting to level that isn't to hard just a bit time consuming, but if you played the game enough you will find ways to make it quicker. Like having certain equipment that helps speed it along or making it easier like gold studs and such. You could also use the Arena of Ages if you have the DS versions to gather capsules to boost your magic, speed, and strength. While you are doing that you would also might find some decent equipment from there.