If you're a sorcerer there's not much point to magic weapon in my opinion. Magic weapon is more for people who are primarily melee and use sorcery/pyromancy/miracles to supplement their offense (or defense). It can only be used on regular weapons, so any weapon that is ascended to magic/fire/lightning/chaos doesn't work with it. With 16 strength and 28 intelligence, you'll be able to get what is - at least in my opinion - the best weapon for magic users. This is Moonlight Greatsword, and you get it from cutting of Seath's tail. You won't encounter him for awhile, and his tail can be a little tough to cut off, but it's definitely worth it. The weapon has "S" scaling with intelligence, which is awesome (the higher your intellect, the more damage you will deal with it). The Moonlight Butterfly Horn is also pretty good. I think it has "B" intelligence scaling, and since it's a spear you can attack from behind a shield. It has a pretty long reach as well.
Of course, given that both weapons deal magic damage, some enemies will not be harmed as much by them. I haven't encountered too many enemies that are super resistant to magic weapons, though. But it's always good to have a fire/lightning (or even just regular) upgraded weapon for backup.
Shield upgrades give the benefit of improving stability. Higher stability means you'll lose less stamina when you block an attack, which lets you block more attacks or have more stamina left to make attacks or your own/roll out of the way.
EDIT: Moonlight Butterfly Horn can be acquired by leveling any spear to +10 and then talking to the giant smith you encounter later in the game. You'll also need the Moonlight Butterfly's Soul for this.
This post has been edited by Defiance: 01 April 2013 - 11:40 PM