You see her in three different outfits in the movie.
The way she looks throughout nearly all of the film
Vanellope's signature "glitch" outfit is a mint green hoodie with a double-layered brown skirt that resembles the wrapping of a peanut-butter cup (many of the girls have skirts like this), green, white and purple leggings, and small black boots. - http://disney.wikia.com/wiki/Vanellope_von_Schweetz
The box art on the arcade (different jacket, racing gloves, and apparently different eyes)
On the side of the Sugar Rush game cabinet, Vanellope can be seen in her royal racing attire which is a teal, orange, and white jumpsuit with brown gloves. In the film's concept art, Vanellope's racing attire comes with a white helmet with a golden crown design detailed onto it. - http://disney.wikia.com/wiki/Vanellope_von_Schweetz
And when the character is reset.
As a princess, Vanellope wore a full skirted glittery long-sleeved gown with lacy white gloves. Her gradient pink petticoat is noticeably covered in pink, white and red gumdrops, sprinkled everywhere like beads...Although she dislikes it, she wore it at Calhoun and Felix's wedding as her maid of honor outfit. -http://disney.wikia.com/wiki/Vanellope_von_Schweetz
So she has her formal wear, as princess, her original royal racing attire, and her glitch appearance, which is the one she prefers and uses.