Also, beyond the mage & cleric lines, I liked using thief certificates as they would give me more agility and thus higher cast speed. Engineer certs will also give some magic critical bonuses. This depends if you go with a build where those aspects are important (and you may abandon those certs at higher level - I'm only 50th).
Speaking of which, you may branch out into other classes too. At first all I played was cleric. Though I've discovered the fun in switching my class just for the fun (not to mention using some of the gear I get that a cleric doesn't use).
If you like mage-type classes, you may enjoy engineer a lot