Watch the WeightWhat to pack for budget travel is always something that comes in for lots of expert comment.
On one hand the stuff you take has to last you for as long as you're away, and on the other you have to carry it about for as long as you're away.
I subscribe to the "take less" strategy - keep leaving stuff out until it's easy to carry. You are not going to the Moon - anything you really need you are going to be able to buy when you get there.
Remember the luggage limit for economy international passengers is 20 kg in the hold, and you can take a small carryon bag (5kg - your day pack?) and a coat into the cabin - if you go over this you could be charged extra - remember, we're talking about budget travel by backpacking here.
There's lots of travel information folks that say you can carry one third of your own body weight in a pack, but I think that after a day carrying that weight you will agree that the airlines idea is better - cut it down to 20kg!
And Australian airports often do check carry-on luggage for both size and weight.
Clothes
On a trip to Queensland it is pretty much guaranteed you will be able to buy anything you want anyway. T shirts and long sleeve cotton shirts are very suitable clothes and they are readily available - cost of shirts ranges from $10 to $100 depending on quality and how smart it is - and for comfort only buy 100% cotton for touring wear.
So just bring the minimum clothes, as well as personal stuff that you really want to carry.
If you are planning on working in office type situations during your stay then you will need some suitable business clothes. Backpacking and the beach is definitely casual wear, but most offices have a smart dress code - particularly in the capital cities. You are also expected to dress smartly for interviews. Again, you could get these clothes here if it suits you.
The other thing that is high on the packing list is boots - Doc Martens or similar - my personal preference is American made Ariat lace-up boots - a bit lighter than Doc Martens, but they last me about a year of day in, day out use on the road - and they look a little smarter than Docs. Ariats lace up over the ankles, are moderately waterproof and if you want to buy them in Oz they will cost around $250.
I know it sounds a bit like harping on - but good, tough, comfortable footwear is just so important - you will spend a lot of time standing and walking, and if your feet are not feeling good it can ruin your day.
Get a light water resistant coat (jacket) with a hood - that is good for use on cool evenings or rainy weather. For Queensland in summer that's all you will need, but if you plan to go on to the southern states then you will need a wool jumper as well.
Washing
Washing clothes is always a thing - most motels and hostels in Queensland will have a laundry - some have soap powder dispenser machines, some don't - trouble is, carrying detergent always seems to end in disaster - and once it's mixed with everything else in your pack it is suprisingly hard to get it out again!
If you use 2 pairs of jeans in rotation, wash the dirty ones in the shower - just wear 'em in there like you forgot to take them off - soap them up with the ordinary soap in the bathroom - also your socks and underclothes.
You won't see it on the travel information sites, but get your mother (grandmother?) to show you how to wring clothes by hand - and you can roll damp clothes in a dry towel and wring them almost dry. Hang them up and it's nearly always possible to dry them overnight. If you wash your undies every night then you always have clean ones - convenient, and avoids stale smells in your pack.
Sundry Stuff
To make it easier to recognise your bag when it comes out on the carousel at the airport, put something distinctive or coloured on it like a ribbon or big sticker.
It is remarkable how handy a few metres of light synthetic cord can be - and one of it's uses can be an improvised clothes line.
I carry a small alarm clock, mainly for insurance when catching 'planes and the such like. Some people like the type of digital watch that has an alarm built in - I haven't used these, but it sounds like a good idea.
Good polarised sunglasses are essential for Queensland - the ones with the side screens look daggy but they are better - your call.
A few cable ties can come in handy - they are very light - great for locking doors on the inside - tieing stuff up - but make sure you have some way to undo them!
Don't know about the business of "sleep sheets" in Australia. I have never used one - spring for a lightweight sleeping bag that un-zips to open right out as a light quilt.
A small towel does take up some space, but you will use it if you have one.
If you can do without anything that needs mains electricity (hair dryer!) then that is a big plus - or you could get one here with the correct fittings for $25.
But if you absolutely need to bring electrical appliances, the power here is 240V 50Hz with a 3 pin plug that is quite different to European outlets - and for US equipment a voltage conversion is also required.
Don't buy an ex-army water bottle - commercial bottled water is available everywhere, so buying those here is one less thing to bring from home.
Get locks with 2 keys and carry them in different places.