Hi Jules! I don't track my expenditure these days, but I estimate my monthly and annual savings (and therefore, expenses) based on how much my net worth goes up each month/year. I was able to predict months in advance what my net worth would be by the end of last year, by a pretty accurate margin, so i think my estimations aren't too far off reality. (Most of my money is still in high interest savings accounts / term deposits at the moment, so there are no wild fluctuations in the net worth to throw off the estimations by too much. I know I should start investing more in shares, though!)
I've posted a budget somewhere else on this forum before, but it has changed a little since then. I pay only $400/month for rent, which really helps - I share a 2-bedroom apartment with a couple. My share of utilities (Electricity, Gas, Water, Internet, Phone) work out around $115/month based on last year's bills. I don't use a heater, it doesn't get that cold here anyway. Private health insurance is $67/month, but there is universal healthcare so it's not absolutely necessary. For things like clothing/shoes, personal care, etc., this will vary, but I don't spend too much on them. I don't have a car, and either walk or take public transport. Even public transport is quite expensive now, and I've started walking to work when the weather is decent enough.
Food can be pricey, but my trick is to go to the markets near closing time, and get discounted fresh produce. My meals are usually based on staples like rice, pasta, noodles. Meat can be part of the dish but I don't tend to use too much of it, plus I tend to go for whatever's cheaper. I still have luxuries like eating out and travelling, I just make sure I don't go too crazy with them. Generally go for meals that are ~$15 every now and then, and travel for less than $2000 per year. (That's about to change though, I'll be quitting my job later this year to travel for months...)
There's another Australian who lives on even less! Check out this recent thread here, it's inspiring:
https://forum.mrmoneymustache.com/ask-a-mustachian/reader-case-study-can-this-artist-semi-retire/ And there are quite a few Australian journals on the forum, too, so check out the Journals section.