Here is a real first stamp.
Catalogues list in value order where there are similar series, but this does not reflect the release dates of different values.
The various colonies of Australia were separate entities until 1901 when they joined to form the Commonwealth of Australia. Australia did not get around to issuing stamps under that banner until 1913 (the well known Kangaroo and Map series). However, there were Australia Postage Dues from 1 July 1902 (they were not used in Victoria though).
So here is a stamp of the first series postmarked on the first day of use.
As I said, a real first. Postmarked Glen Osmond 1 July, 1902.