There is a version of English, which is not Runglish, Chinglish or whatever, but English spoken by a lot of educated foreigners who speak English well and don't belong to an English-speaking country. They concentrate on getting their pronunciation right, probably closer to British but some have some American sound to it. Spelling is slightly different but it's OK to use either, as long as you're consistent. American accent can be good too if you speak like a TV commentator, not like a bus driver. So a foreigner (French, German, Russian, Chinese, whatever) who mastered English may choose correct British or correct American accent.

Australian local accent does sound a bit undeducated but many Australian fix their accents and speak very decently without "ockering". Fro example TV reporters speak very good English in Australia and I enjoy their English more than those on CNN.

Your Englsih will develop as you use it, the words and phrases you pick up depend on sources you use, so you may be influenced by American, British or other source, it's all English. I would focus on words and phrases understood by all English speakers first - slang words are just innumerable, they change all the time and may not be understood by other English speakers. Read English books/sites you like without bothering too much, which version it is and you will get most of it.