Well, I still haven't finished my first game, but I had several 'trial runs' but I settled on my current leader.
I chose a Cleric, because, simply, I wanted a good healer (I'm a bit of a hack&slash player :fight

.
HOWEVER, as they advance in level, Clerics get some EXCELLENT offensive spells, which makes her better than my lower-level dual & multi Mages (she is lvl 20 at present while Aerie & Imoen are around lvl 13).
So, although I lack the experience of playing with a High level mage (Next time!

) I can definitely recommend a Cleric for a new player. Just make sure you give him/her 18 Wisdom plus as high as you can Strength and Constitution. DON'T settle for less than 90 total score on you Ability Rolls at character creation!
F.
F.