I think it would be safe to say that psychedelic substances would be the substances of choice within the 'doof' community, with LSD probably taking centre stage, closely followed by MDMA. It is honestly difficult to give an accurate answer as it would depend on so many factors including location, time of year, current availability and people attending.
As for saying Research Chemicals are rare within Australia, it's hard to say. How do you define a rare drug??? As with any substance, access is made easier through connections. The psychedelic community within Australia is reasonably small and some would even describe it as close knit. I would suggest within these communities, Research Chemicals may be easier to come across then other substances. As always, it comes down to who you know.