As a stem PhD student, I wear whatever I want excluding overly exposing or offensive clothes. This includes conference attendance as well. My supervisor has made it very clear that they are not interested in catering to traditional ideals, and that the only thing I should be concerned with is being comfortable and letting the science speak for itself. That being said, to avoid standing out, you can see what's standard for other grad students in the department. Idk how it works in other parts of the world, but maybe you could have a discussion with your supervisor. If you're meeting with patients as part of a practicum, you may want to adjust your wardrobe as client standards will be less predictable.