I want to rp as a Thalmor wizard. It is my first time playing a pure mage, I usually play as a hybrid (Combat, heavy armor and magic.) I was wondering what schools and perks should I invest in?

If you are going pure mage then you probably want Enchanting for magic reduction, destruction+impact to stunlock enemies,conjuration to get an ally for enemies to focus on, and alteration for mage armor. That's what i recommend anyway.

Invest heavily in Destruction and that Impact perk, makes things a lot easier. If your truly doing a true mage, then focus on all the schools. I know Restoration has some good perks that benefit mages (like increased magicka or something). Sorry, haven't played the game in a while and don't have access to perk trees right now. Good luck with your mage though!