Hahah all you need is yourself!
I interviewed at UIW pretty recently and they provided a notepad and water. It was closed file so the interviewer just asked you questions, no need for your transcript or anything-- I didn't see any other applicants with that. They should have what they want to look at if it's open file (transcript, personal statement etc). If it's closed file then I think they just want to get to know you.
I also had a little bag with me that had my phone and wallet, that's all 🙂