See post #3385915 for her default outfit.
Her default outfit, fitting for her JK lore, is a school uniform consisting of a white double-breasted blazer, white bow, black skirt, and white thighhighs. Her hair is tied into twintails held by red bows, while she is portrayed with red eyes (can also be purple).
For her other official alternate costumes, see their corresponding tags:
She is portrayed in her lore as a lady high school student of a private magic academy, Teika High School. In addition, she has a strong personality and is interested in classical music, and is also an otaku.