Early on, while your still weak and vulnerable, learn use and abuse Sunfire and Melf's Meteors. The former ignores magic resistance IIRC and can hit improved invisible creatures you can't otherwise target with spells (think spirit trolls and Torgal). With the latter, you can fell even Adamantine Golems. Wicked wicked wicked.
Sorcerors are probably one of the easiest classes to solo. Challenging only in the beginning, after you get Project Image and the Lvl 8 & 9 spells, you are a killing machine
~~ aim low, deliver.