Here's a couple of my favourites:
"Not here to fuck spiders" => Not here to waste time
"Mad as a cut snake" => Very angry
"Busier than a one armed brickie in Baghdad" => Very busy (a brickie is a bricklayer)
"Built like a brick shithouse" => A large, muscular man
"Crack the shits" => get annoyed
"Dog act" => something done to a friend that's uncalled for, e.g. skipping your round at the pub
"Stitch up" => A scam or a trick
"Sick cunt" => An outstanding person
"Old mate" => Someone who's not your friend
"Smoko" => Morning break at work
"Misso" => Girlfriend (short for missus)
"Ambo" => Paramedic (short for ambulance)
"Servo" => Service Station (gas station for Americans)
"Seppo" => American
"Pokies" => Poker machines
"Yeah nah" => either yes, or no, depending on context. Can also be used as filler in a sentence.
This leads to beautiful sentences, such as:
"Yeah nah, the misso cracked the shits at me 'cause I spent the whole arvo at the pokies"
Here's a decent sized list of Aussie slang: https://nomadsworld.com/aussie-slang/