Welcome to Eorzea!

What server you play on is up to you - the JP servers are closer to Australia naturally so time differences are not as bad as the NA/EU servers. But as they naturally have a much larger JP player base communication can be an issue, although a lot of JP players do understand English.

I'm Australian too (Perth, WA) and I play on a JP server with no real problems. But if you're happy enough on Cerberus then it might be better to stay with a NA/EU server instead of changing, especially if you've already made friends there . You can actually move your existing character to another server too, but it's a paid service that costs money to do so.

Hopefully this has helped.