aim for 98.5+ ATAR and 93rd %ile+ UMAT (assuming you performly relatively evenly across all sections). it helps if you also live in GWS
frankly, you're going to need to be able to study properly to get through medicine, it is a content-heavy course. it is nice to think that being kind and versatile and all those other qualities is enough to make you a good doctor, but it's all useless if you're unwilling/unable to memorise all the medical knowledge (which dwarfs however much you'll learn in the HSC).
of course, i definitely don't mean to scare anyone away from the course. if you have a decent work ethic, you'll adapt. if you don't, you're fucked