Your Sim was born a spell caster in a human family and has no teacher, so if they want to learn magic they must study by themselves. They have their own dream to pursue, it might not be magic, but magic tends to pop up in their life.
With the bb.showhiddenobjects cheat, you can access all the different types of wands and brooms, so your sim could just find something and say, hey that could be my wand or broom from now on.
With vampires, my vampires were usually trying to get something besides being vampires. Make a close friend, fall in love, become a writer, raise a kid, or even just survive. It depended on the game and the story. They just happened to be a vampire while dealing with all this.
