As publically promoted, the core business of RAAus is to:
• Provide Australians with a safe, accessible and cost effective form of aviation.
• Inspire Australians to participate in all forms of aviation, and connect these people to a like-minded community.
• Register aircraft including three-axis aircraft, weightshift microlights, and powered parachutes.
• Allow aircraft owners and maintainers to maintain, repair and modify aircraft registered by RAAus.
• Support members that design and build their own aircraft.
• Certify pilots to operate aircraft registered with RAAus.
• Authorise instructors to train pilots.
• Develop training material for instructors to deliver.
• Educate members and actively promote safety.
If you are specifically seeking advocacy, I think joining AOPA would be a better bet.