If you decided to become a mage, you will have to get one out of two solutions (Payon/Morroc Solution) for the potion you have to mix if you want to get approved. Instead of walking to Payon or Morroc, which are REALLY far away from Geffen (the city where you become a mage), talk to a Merchant or a Swordman in the Mage School. They usually sell Payon and Morroc Solutions at a low price of 300 zenny. Good luck!