Hurray, my Armorer skill just hit 50. I can finally repair magic items myself! That's going to save me 2000 to 3000 gold per Oblivion gate.
One thing I've been doing to raise my magic skills is buying low level spells and casting them as I run around. I have a small shield spell to raise alteration (for lock picking) and a starlight spell to raise illusion, I think it was. I just keep casting them as I go around doing my thing.
That's the best way, but be aware it takes a long long time for any skills that aren't your primary skills to increase. I tried the alteration method but the locks I found went to hard/very hard much faster than my skill did. So I went back to carry 100 lockpicks at a time.
But I could upgrade my feather spell, if I can ever find the person who sells the next level again.