I play a mage too. Now level 40...
For weapon; I use daggers from beginning however there are not much of them. I bought "Wizard's Long Dagger of Cold" from Geoff when I get to Ars Magicana. Until then used one or another. Now holding on "Small Nobleman's Dagger" as well as the one above. I also have the "Short Sword" which has 5 charm slot and some good stuff, in stock. With right enchantments it will be really powerful, I think.
For armor; I use every slot available including shield. I have nearly 90 STR because I play as a battlemage. With that STR points I can use every piece of armor in game. By now I have 3 pieces from "Dragon Armor" set(Shield, Belt and Gloves), Armor of Larian. All of them are quest items and they are very powerful.
Just a little piece of advice:
Do not let your STR and AGI become too low. Develop your mage in a way that he can handle himself for at least a few seconds, the game is not that easy.
BTW, the game is great, enjoy it...
