VPN! https://thatoneprivacysite.net is a good place to start searching for a good one. Tor is another option that does the same thing as far as we care.
Account Creation: 10 Minute Mail and friends for a burner email to make your account (if socmed providers want a phone number you’re out of luck afaik, I don’t know if its possible to get a burner phone in Australia)
Passwords: Without an email address to fall back on, use a god damned password manager!
Communications: GPG for emails and Signal for texts/calls.
Pseudonym/Profile Pic: Your name should be completely unrelated to you, and you should have a profile picture (because people filter non-profile pics out), again make sure it has nothing to do with you.
And compartmentalise your activism from your non activism as much as possible, to avoid other sites tracking you.
Pretty much rip off the Data Retention guide and update it.
Obviously this depends on your threat model, not all of the above is required as long as the government isn’t actively looking for the anti-agenda people. As long as they aren’t doing that, a pseudonym that you don’t use anywhere else and is completely unconnected with you is probably enough.