well... depends on level i suppose. Fire is definitely a zerks bread and butter, it can depend on if other players have any marks. A lot of people in my fighting bracket have reflection against chaos so I don't use it much anymore. I use fire mostly, except against other zerks because they can possibly have reflection against it. I like to dot with fire chain to weaken the other opponents magic. That's a good benefit of having fire magic.
I don't use air at all. Stick to fire and chaos depending on situation mate.

Thank you for your reply. Right now I will be focusing on leveling my fire because chaos magic is too expensive for my level but later I will do as you do.
Thank you very much.