You do realise that Fantasia's are there to redesign your character appearance right? It's not like they add anything game breaking or enhancing, and thus they should never need to be used more than a few times.

You get two of them by simply playing the game and being registered. Mine are still kicking back on my retainer because I've no desire to change perfection. That said, should you ever want to change your race, SE already has you covered with the freebie Fantasias.

Is there a particular reason why anyone would actually need to constantly change their race?