For low level wizards, I believe the spell Mage Armor gives you + 4 to your AC until you rest(meaning you have it on at the start of a battle), which helps a great deal against bowmen and the like. (Or am I confusing this with how it will be in KOTC2?
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Constitution is really important. A wizard gets 1-4 hit points per level. Constitution 18 gives you 4 extra hit points per level, effectively doubling your hit points compared to constitution 10. Second most useful stat for wizards.(some might argue that Con is more important than Int in a table top game, but for KOTC, Con is second)
I feel that for crafting magic stuff, you want to do it sparingly in the start(a cure light wounds wand or two perhaps), but once you hit level 9 or so, you should craft as much stuff as you can. Before that, the stuff you can craft isn't that good compared to the loot you find from enemies, but around that level, it becomes the opposite. The stuff you craft is far superior to what you can find, especially since you can fine tune the items to fit your characters.
Going too crazy with crafting will lead your crafters to be even several levels below your non-crafting guys. This isn't a problem since you actually get comparative experience, if I remember correctly. Meaning, a level 10 char will get less exp than a level 9 char for the same encounter. So catching up isn't that bad, but being two levels lower than the rest, especially if your wizard is the crafter instead of the cleric, can have devastating results on your ability to deal with powerful foes or a lot of weak ones, since high level wizard spells are super powerful.