Everyone, as previously stated in the explanation of Cinderfells Magic, contains an Aura- some holding just one aura while many could harbour more. This is all decided through Aura points. In Cinderfell, you can't cast every single magic that comes to mind; as that is too much for one single person to handle.. Your Aura, and aura types, are limited.
Everyone has 3 full aura points that they can use, and select different circles of magic to learn or be able to cast with these points. In the section/s regarding Magical Circles, Each Circle of Magic will have a cost price. This cost is met by paying with your Aura points. For example, If I wanted to learn Arcane magic, and it cost 1 Aura point, I would use one of my Aura points to be able to cast Arcane. This leaves 2 aura points left for me to decide on any other magic circle/s i wish to learn, some which have subclasses to choose from such as Elementalism.
Areas that have Subclasses may only require 1 or 2 full aura points as a cost, but only allow you to pick 3 of the subclasses with that point. They will state how many sub points you get, and how many you may choose.