Show your best and most professional self.
While it's important to be your authentic self, it's equally important to present a professional image of yourself to prospective employers. The reality is that there are certain expectations in the work work world.
Althought it's true that the official or unofficial dress code in each work place can vary, when you go to an interview, you want your appearance to show that you cared enough about getting the job to make an effort to look good (and appropriate) for the interview. Also, you want it to be easy for the employer to picture you working with their other employers and especially their customers. Looking a little more polished than you might normally look every day on the job you are applying for is generally the way to go.
Avoid wearing clothes that are torn, and that don't fit right. They should be clean and ironed - if necessary. It's also important to dress appropriately for the job. For example, it's not wise to wear a suit to an interview at a garage or coveralls to an interview at a restaurant.