Obviously, you'll need your relatively plain, solid color dress. Add a clutch- preferably in a punchy color or pattern, eye catching is a good rule of thumb. You'll need a bold lip; a deep, vampy red or a bright one- the choice is yours! Statement jewelry can be very cheap if you buy it from places like Forever 21 or a costume shop, you'll need a some, whether it's ear cuffs or rings! A blazer- shrunken, fitted, black, navy- whatever it is, put it on top of your dress because a) it can get chilly wherever you're going and b) it adds a professional touch to your ensemble.
Sorry this post is so short, but I hope it was helpful! Have a lovely day, xoxo