Packing...

Well finally we did a FaceTime session only for packing my suitcase or rather deciding what I'm going to take to Australia and eventually after I was worried that all my stuff won't fit into my new 120l suitcase it did and I still have space but the whole damn suitcase is now 25.1kg which is kind of good but still stupid 3.1kg too much and who knows how the wage at the airport is configured!?! So what am I going to take into my hand luggage which is at the moment only a bag and my ticket, medicine, some uni things, iPad and cables and nothing else.
Should I take a summer outfit just in case my bag get lost (as it tend to) and maybe my cameras?
Too many questions!