You'll mostly live in pjs if not out in the evening. Jeans and a hoodie will be fine, if you travel in that, then less to pack. I spend most of my time in lined leggings that I wear as a base layer and a hoodie.
We budget about £100 a day on holiday, both summer and ski. Actual day to day spend can vary. Have some money ready for clothing emergencies as its expensive in resort for these things (lost gloves/goggles/buff).
Presumably you'll be hiring equipment? We do too. But we take our own helmets. No-one else's sweaty head has graced it, and I know it hasn't been in a fall.
Exercises. Anything where you can work your thighs and leg muscles. Squats I'm afraid. Having a good core will help too with balance. You'll spend a lot of time in a sort of half squat position that leans when you want to turn.
You'll wonder on day 3 what on earth you were thinking, when muscles you didn't know you had start screaming, but honestly, it's so worth it.
If the place you're staying at has a sauna and a pool, use it! I love the sauna for relaxing the muscles that have worked hard.
Have an amazing time. It is the best holiday ever.