When you betray what are you able to take with you? I have heard that you lose your upgraded spells but what about gear or money? or the rest of the things in your bags? Any help is appreciated.
you can keep everything you can carry. Your spells are all stripped away because technically, your class is changed. Even if your class is available on both sides, the game sees a difference between, say warden/Qeynos and warden/Freeport
The only items you would loose is what is in the shared bank acount if you dont have any other characters in the city(that you're betraying) Or if you leave stuff in your house in old city and cant sneak back in to retrieve it.