Best thing to do if you want to level quickly is get 3 fire types with low speed and high attack power and one water element that's faster than the fire types, all with GS skill and low level horses.

Fire uses
1st round: slowdown
2nd round: Hot Fire (self)
3rd round: Attack with Hagendis Hit

Water uses
1st round: Shrink
2nd round: Freeze
3rd round: Sleep

Might I also suggest that those fire types have weapons with a critical chance :)

I did some bursting earlier today. Normally the two fires I was using do about 5 or 6k damage combined to wind frogs. they both have a crit weapon though and when they crit they do 12k total combo damage with just two fire types and no shrink spell on the target! O_o . Fire got over 1.5k exp when that happened and water got over 3.1k exp.

I still need to get gs for my water character :(