The same phrase can have different meanings in different English-speaking countries or in different social situations. In my experience, it is a negative phrase used to mock someone who wants praise for a trivial accomplishment. "Good job!" "Good work!" is common for a positive phrase.

"Good for you" can be used both in a positive sense (as a complement when someone has done something well) or in a negative sense (as sarcasm, or to mock someone who has done something that they should not have done). Whether a speaker is using it in the positive sense or the negative sense will be conveyed by the tone of their voice.

Positive scenario (Mary is impressed by Jack's decision) Jack: I'm done with this job. Tomorrow I'm going to hand in my resignation and them I'm going to open my own restaurant. Mary: Good for you, Jack. Negative scenario (Jane isn't so happy to see Chris) Chris: Jane, I've missed you so much! Jane: Good for you, Chris. Negative scenario (Steve isn't impressed by Jim's sales techniques) Jim: ... and then I told her "of course you'll make your money back in no time". And she believed me! Ha! Steve: Good for you, Jim.