I had some brilliant advise given to me last year.

Always wear more layers than less, if you start to get to warm you can always loose a layer into a coat pocket/back pack or locker. If the waether turns then you have it to put back on if needed.

I had a bloke on my ski school last year that was sent to go dress properly by the instructor as he had a tshirt on under his jacket. The wind chill at the top of the mountain was -38. soft sod would have frozen...

have fun you will love it,

I wear themals under my ski pants these are the same as wearing leggings if you have a few pairs of those. Top half I have a long sleeve T-shirt, short sleeve T-shirt, thin fleece, hoody and coat.... depending on the weather any concoction of the top half items. I don't actually own any top thermals as such T-shirts do the same job for me and much cheaper. As Lefty says as long as you have a few layers you can play around with you'll be fine