I went in February 2019 for 12 days, solo. Flew into Gold Coast and out of Melbourne and went to Brisbane, Sydney and Hobart in between. AUD300 in my wallet, 3 credit cards. People don't need to spend as much as you think, groceries are, fast food is ok too. I did have my Employment confirmation letter, my salary slips, my bank account statement, all my hotel bookings, car rental booking on standby though just in case they asked. Didn't spend more than 50 minutes at the immigration counter in Gold Coast airport too. The only thing they asked me was I ticked yes on a question, to declare some meds I brought with me. Thing is in their for meds, weapon etc is under 1 declaration, So I just had to clarify that it was meds. I also checked every week on my visa status from the point I got my ETA to the time I left to ensure that it is still in place.