Illusion is my favorite school of magic. I love casting Fury on enemies and watching them attack each other so I have fewer to deal with in the end. Calm is useful for getting out of combat quickly (usually so you can run the eff away), Fear for making the enemy run the eff away from you (this, and Calm, are great crowd control, temporarily reducing the number of enemies you have to deal with simultaneously), and then Muffle and Invisibility have their own obvious benefits; no one can hear you, and no one can see you.
It takes a particular mindset and character goal set to get in the habit of using and enjoying magic, though. For your first playthrough, I say try anything, and do whatever you want HOWever you want. It took me three or four attempts before I found the character and mindset that would carry me through the game. She's still my favorite and longest-lived character, and my namesake. I explored most options in the game with her and built an elaborate narrative in my head as I went along.
If you're prone to doing the same, there are a couple of things to note for the forum: If you write your adventures in a Journal style and follow the exact events of the game, we ask that you post those in your personal blog. If what you've written is more narrative fiction (whether it incorporates the game's events or not), it should go in the Fan Fiction section, even if it's written in first person, OR uses a journal or "Letter to a Friend" format; as long as it is more story than someone observing the world in first person, per day, it can probably live in Fan Fiction.
I have no idea if that's something that would ultimately interest you, but you'd be surprised how many people didn't start out thinking they'd write fan fiction, and end up posting their stories here.
So, welcome to the forum! Welcome to the game! Feel free to stop in and chat in the shoutbox whenever you're free!