“Good on ya” Means “Well Done”

“Good on ya” is a relaxed Australian pronunciation of “Good on you”. It usually means “well done” or “good work”, showing approval of someone’s effort, choice or action. It should not be translated literally.

For example: A: I finished the safety course today. B: Good on ya — that took some work. “Well done” is more neutral. “Good for you” can express sincere approval, but depending on variety and tone it may sound distant or sarcastic, so it is not an automatic substitute. “Good on ya” can also be sarcastic when the tone makes that clear.

https://www.abc.net.au/education/learn-english/learn-english-weird-and-wonderful-aussie-slang-terms/8036750
https://www.collinsdictionary.com/dictionary/english/good-on-you