It's not even a question, wear a suit. If you get a job there, that's what you'll be wearing except you'll be wearing their suits aka the good stuff. You'll get an allowance for that so you won't have to pay yourself. I mention this since a lot wonder how do SAs afford to wear the stuff themselves.
Make sure the suit is good fitting. You don't have to break the bank as well. Fast fashion brands will suffice.
Prep up, know about the brand, its history, its current projects and if you really want to wow them pull up the 10k statement and tell them how the firm is doing compared to previous years.
