I was told just to bring a cc and a driver's license; the first day is generally the most restrictive in terms of what you can bring inside. To be safe, I would not bring anything you cannot tuck inside your jean's back pocket. Not sure about a jacket but it has been cool lately so I fully intend to wear adequate clothing to stay warm.
It used to not be this way- people routinely arrived with their birkins, kellys, etc.- I guess there have been problems with inventory loss. I am hoping the cash registers do not go on the fritz- it can get very claustrophobic on the 3rd floor- no windows with lots of bodies pushing and shoving. It does quiet down considerably after the first day.