Try to get the Mana Shield spell as soon as you can. The Mana Shield allows you to take damage from your Mana pool, rather than your hit points and is useful to have, especially when faced with a horde or a group of missile-equipped monsters or ranged spell-casters.
Look for weapons and equipment with some magic enhancing characteristics as you'll receive double bonuses for them
Rings and amulets that increase strength will allow you to wear some decent armor as you progress into the tougher areas of the game.
Try to balance your spells between close-range spells and ranged spells. If you stack your Sorcerer towards spells designed for close-in use, such as Flash you'll be less effective if you need to deal with a horde at a distance.
Mana potions are your friend; even more so than healing potions, especially if you have Mana Shield. Make sure you stock up regularly.