Most Helpful Girl
I was in Germany this past summer-- ah, how I wish to return!
Be aware that the temperature will be considerably chilly, particularly if you are from an area of frequent warmth. As I write this, Munich is 32° and snowing.
You could certainly purchase a few garments upon your arrival (which would also help disguise you from appearing too much like a tourist)... though, depending on where you are departing from, the exchange-rate may be murder.
Various outer coats (I am fond of wool-- but it does not matter); be sure to put to thought the elements (in other words: consider if an item will potentially be easily ruined); sweaters are good to layer (which I have noticed Germans wearing, to add); long-sleeved shirts; long-pants; comfortable shoes... you may also find it wise to invest in a hat (which will assist in protecting the location that loses the most heat, of course); gloves may prove to be a good decision, depending on how often you plan to be in the outdoors.
A winter scarf may be an intelligent buy, too.
I wish you the best!