In addition to normal magic Spheres of Power are allowed. The rules of magic are less rigid in Gæteia after the connection to many planes and deities were lost. No longer do the gods systematically concentrate magic into certain spells to the same extent that they did before. Rules wise using spheres of power is more thematically fitting, especially for spontaneous casters.
If interested you may also use a mixture of standard magic and spheres of power, by making spheres of power abilities into spells. Contact me for this though.
If using SoP it is preferable if you use the standard casting traditions. (can be found here http://spheresofpower.wikidot.com/casting-traditions – ctrl f Suggested Traditions for Non-Spherecasting Classes)