well, if your pure int, you WANT to get armour. protects your hp since it will be low.
and really, there is no best choice, but the one i would
recomend would be int. your magical attacks will be a lot stronger, but your phy.
def would be a lot less. you can kill something your lvl with in bout 2 or 3 hits, but it can kill you in about 4 - 5 hits. so there are some ups and downs.
i know you want the best choice, but there is none really. its
your choice. str you have more hp and stronger attcks w/o magic and youll have low mag. balance which is bad if you want to be a nuker
int you have much stronger magic attacks but a LOT less hp. and int is the
only way to go to be a pawning nuker
so i would suggest int but i am pure str, but it is totally up to you. measure the odds and see which one you like the most, and do NOT be hybrid!
pure int use armour set and pure str use garment set, so switch to armour if your going to be pure int.