In my opinion, all of the AoS electives Journeys, Belonging, Discovery are quite similar in the sense that it's a process which usually pertains to a transformation of self, so what I would recommend doing is basically getting your hands on the Journey rubrics which your school uses (you can really just look up the AoS Journeys from ages ago as your school will most likely copy this or you can ask a student from the grade above for their copy) and then deconstruct it and think of questions they can ask (you can also look up past HSC AoS journey questions) and try and see what kind of thesis you are going to argue about (but this is hard without prescribed texts so try and find one what you have and read it). Other than that, there really isn't too much worth going ahead on, I would recommend spending time on Maths and Science as you know exactly what's going to be assessed
