Hello and welcome
We have the Avicultural Society of WA (open days in Belmont on the last Sunday of every month, except December) and the Finch Society (meets in Osborne Park on the 4th Tuesday of the month)

bushranger or silverfox are probably the best people to tell you about the Finch Society as they're members!!
I would also say that spanna would be a good person to see re: non mutation gouldians. Though myself and Kylie have just had our first clutch of non mutation gouldians ;D