best mobile phone under $300.00 Aust

Are you looking to get it on contract, or off contract? Off contract, that budget will probably allow you to get a phone that is 1-2 years old, maybe a 3-year old phone if you want a major flagship phone. If you want to get it on contract, or if you have some kind of upgrade plan available, that might let you purchase a more recent phone at that price. There are also some cheaper options, like the Moto G--they often have the equivalent specs of a flagship that is a year or two old but are still very good phones for most people.

I think your best bet would be to look at some older phones. Not sure of prices in Australia, but I know you can get a Samsung Galaxy S4 for $99 on contract, or $199 as part of a carrier upgrade here in the U.S.; that's a solid price for a phone that is still very good and usable. Even the S3 is still a viable option, and is dirt cheap at this point. The Nexus 5 is also a great option, but might be a little over your budget.