1) Get ready for a match
2) Wait about 10 seconds before the match starts
3) Cast rank 1 Blizzard a few times
4) You will have Arcane Potency as your starter spell.

If that doesn't work and you need gold quick, I recommend The MMORPG Exchange WoW Gold. They deliver quickly and are cheap! I usually receive my gold within 20 minutes. They're my secret weapon, I highly recommend them!