You need to bring ALL the documents that you submitted with your application.
If you used SimpleCitizen to make your application, they usually will mail you a whole folder with the documents you will send out to your local office. Before you send them I would recommend making a copy of this folder. I didn’t think about doing this so I needed to reprint them all from the PDF that they provided.
If you think there are any other documents that will help your case I would bring them too. I brought pictures, a driver’s license ID that I had not provided when I submitted my file and a few extra documents like pay stubs from a job different than the one my husband had when we submitted our application.
Good luck at your interview!