"Good for you" is literally something that is good for you. It is being said if someone is happy for you (although sometimes it is said in a sarcastic way). This is usually being used in British English. "Good on you" is more of an Australian saying. However, both sayings are for informal conversations. You should avoid using both in a formal conversation. In that case "I'm glad to hear that" is more common.

Hey Ethan, 1) People say ''Good on you!'' to show that they admire something you have done. This expression is used as an exclamation of approval towards someone, especially for something that they have achieved (chiefly Australian). E.g.: ''I go swimming every day now.'' ''Wow, good on you, my friend!'' E.g.: ''I just got a promotion!'' ''That is great! Good on you!'' As for ''Good for you!'', it is used as a complimentary expression of encouragement for something that someone has done or received (chiefly British). E.g.: ''Good for you! You passed the exam.'' E.g.: ''I finally got a raise.'' ''Oh, good for you!'' ***NOTICE: ''Good for you!'' is not necessarily said in a sarcastic manner. Hope that helps!!!

I English Good for You means that it is healthy for you ie. Vegetables are good for you. good on you is eg The coat looks good on you

In addition to what Kevin just said below/above, 'good on you' is also a very British saying. We use it here a lot.