Bring as many outfits as you can comfortably transport! My colleague Judy Babinski recommends that women bring at least 6 outfits, a mixture of casual and business. Note that you only need to think about the wardrobe will show in your headshot (tops, jackets, etc.). It’s great to have many choices, because clothing reads differently on camera than when you look in the mirror, and we’ll want to experiment and pick the clear winners for your headshots. Please make sure everything is clean and pressed.
If in doubt about whether or not to bring a wardrobe item, I’d say just bring it. It’s better to have too much than to be regretting you didn’t bring something.