From Longman Dictionary of Contemporary Englishgood for somebodygood for somebodyused to say that you approve of something that someone has done ‘I’ve decided to accept the job.’ ‘Good for you.’ → good
Examples from the Corpus
good for somebody• Not much good for anything else.• So Princeton looked good for college until I met their pretentious admissions rep.• Life in Solano County had been good for him and Annette, he said.• This was good for his journalism.• The buffalo robes were good for keeping warm in carriages in northern cities.• The more physical the better for me.• Armed with inadequate information he usually fails to see why one moment is better for putting in a tack than any other.• She lost the first two babies, you know that, and she's always done her best for you. 