Larian Studios Forums Divinity - Original Sin Divinity - Original Sin - General Best character builds - for you (spoilers)

There are few useful Talents that you can pick as a mage, just respec them and trade everything but Glass Cannon for an additional 60 Ability points / 12 Attribute points.

Also if you are playing with Glass Cannon, it is sometimes useful to not invest an Attribute point right away , because your maximum AP have to be >= your turn AP. With 7 SPD and 7 CON you have 14 AP but for the next bonus you need to increase both attributes to 9. If you save some points you can be more flexible depending on the gear that you will find until you can actually benefit from the attribute increase.