Instead of using a real mage, choose any of the creatures in Arena whose levels add up to 6 to be your "mage". Your training must be the same as your mage's schools. If your creature is not trained in a major school,
It may gain training in its subtype in addition to its minor school training.
If your Mage includes a familiar, you have 9 channeling. Otherwise you have 10 channeling. Spellbook size is still 120 points. This is true even if your mage is made up of more than one creature. An equipment can only target and be attached to one "mage" creature at a time.
Other than that, the rules are the same as normal. Enjoy!