I am not sure what to do to get ready for my job interview.
Make sure that you understand the company. Do you understand what it is that they do?
No, I probably need to do some more research.
When you've finished your research it will help you figure out whether your company is rigid in philosophy or kind of more relaxed. Does that make sense?
I think that their attitude is rather casual.
So all of that information will help you to pick out what to wear. Do you have something to wear?
I have absolutely nothing so far.
You know I could go shopping with you sometime if you need it, but can we talk about other basics?
Yes, where should we go from here?
Focus on being relaxed and open, don't forget to smile and shake hands and be genuinely interested in what their company is about. I'm sure you'll do well.