myth is a good school because you will get lots of minion and there isn't many myth monster. there is a few in wizardcity and in mooshu the only problem is your teacher but myth is a really great school
storm is also a good school the strongest attack but low accury (spelled it wrong) but you will get spell for that to incrase it and if you choose balance for second school that will boost it more storm is also fun
Most people would answer on opinion, but not fact. Truth is, they're both pretty amazing. In my opinion, storm is the best because of its power. Of course, it does fizzle a lot. That is a flaw. Myth is storm's opposite and is mostly about minions. I think the first spell you learn is a golem minion spell! So it depends on what you think you like better.
Maybe someone else can give you some better ideas on which to use. Hope that helped.
All of the wizard schools have benefits and weaknesses. For example, Storm has very powerful spells but fails casting them a high percentage of time.
The best response would be to make up one of each and play them to see what fits your own 'gaming' style. There is no rush here, have fun at the lower levels and get a feel for your character and his/her spells and abilities.