"Good to you" could be used in 1) "He is so good to you", meaning that he treats you well, which usually includes buying you things, being a good friend, or whatever else; 2) "Does it taste good to you?" In this case, something that is "good to YOU" is based on your opinion. Another example: "That sounds good to me" (in response to someone's idea, for example). "Good for you" also has two meanings. 1) "Eat your vegetables. They are good for you." This is something that benefits you. "Go take a walk. The fresh air will be good for you." 2) We can use this as a set phrase (a (maybe common) phrase that works by itself). In this case, "Good for you" basically means "I don't care" or "I'm happy for you". The first one is probably used more by younger people and the difference of meaning is in the tone. If it sounds nice and sincere, it means "I'm happy for you"; if it sounds rude, bored, or sarcastic (not serious), then it means "I don't care". I hope that helps :)

"Good for you" describes how a situation/something benefits someone. "Good to you" describes how someone's actions benefits someone. E.G.(1): "I've found a new job, and it comes with all these benefits!" "Good for you, man." In this example, the response talks about how the new job is benefiting person 1. E.G.(2): "I think I might break up with her...but she's been so good to me" In this example, the response talks about how "she" has been "good" to the speaker, how she benefited him. Hope this kind of makes sense!