Firstly, Welcome to Ironworks! [img]graemlins/thewave.gif[/img]
As for your first solo, mine was a straight mage, but if you want to cover all your bases, you could try the 'Swiss army knife' Fighter/Mage/Thief. Although this is a bit limiting with only SoA installed, if you have ToB, it can be a very powerful class.
I would recomend using a sorcerer only if you know the spell system very well. As for your spell picks, you could look at Dundee Slaytern's Solo Sorcerer Spell List, which can be found
Baldur's Gate II - Spells Reference is an excelent resource on all manner of tactics and cheese.