good luck vs blessing

good luck and blessing both are nouns.

Word	Noun	Adjective	Verb	Adverb
good luck	Yes	No	No	No
blessing	Yes	No	No	No

As nouns, blessing is a hyponym of good luck; that is, blessing is a word with a more specific, narrower meaning than good luck:

Other hyponyms of good luck include prosperity, successfulness, boon.

good luck (noun)	blessing (noun)
an unexpected piece of good luck	the act of praying for divine protection
a stroke of luck	the formal act of approving
an auspicious state resulting from favorable outcomes	a ceremonial prayer invoking divine protection
	a short prayer of thanks before a meal
	a desirable state