Without the expansions, there are 8 stages. These last around 5-10 minutes each at first. After you beat all 8 stages with the 6 classes (any gender), you unlock *spoilers?*novice*spoilers?*. Once you beat the game with that, you unlock a 9th stage.
If you get the expansions, you get a bunch of new stages AND arena mode, which vary in length.
Overall, the game isn't terribly long, but it's very fun trying out new characters and character builds. For example, Double Attack (thief) actually makes a ghostly image of yourself that follow your for a while and mimics your movements! (Doing half your damage!) Couple that with a female thief (fastest class) and high agility and you have a blazing fast (before the expansions, female thieves could outrun the screen) double hitting character. That's only one build! You can also make a mage that spams Ice Bolt (drops 1 * Ice Bolt Level... bolts in randomly locations. If you max it, you get 10 Ice Bolts that drop randomly. Spam it for a cool effect!)
And so on! Check out ragnarokbattle.com for guides and stuff...
Character Simulator: http://www.pages.drexel.edu/~tds35/simulator/
(Click the character's NAME to change class/gender. Skills have skill requirements... If you're wondering why there are only a few skills there right now. If you've played RO, I think the requirements are the same so this should be familiar. Max level is 30 IF you have the expansions.)





