How do you find out what is the proper dress for a given job/company/industry? You can call the Human Resources office where you are interviewing and simply ask. Or, you could visit the company’s office to retrieve an application or other company information and observe the attire current employees are wearing — though make sure you are not there on a “casual day” and misinterpret the dress code.
Finally, do you need to run out and spend a lot of money on clothes for interviewing? No, but you should make sure you have at least two professional sets of attire. You’ll need more than that, but depending on your current financial condition, two is enough to get started and you can buy more once you have the job or have more financial resources.