運が向く (un ga muku): fortune smiles, one's luck turns one's way. 運 (un) is fortune, luck, the way things are going to fall; が (ga) marks it as the subject; 向く (muku) is to face, to turn toward, so the phrase says literally
luck turns toward me, and the dictionaries define it as good luck coming one's way, circumstances turning for the better. It is spoken Japanese, an idiom of the Edo stage and the storyteller's hall, the line a character says when the tide of a life turns:
there, my luck has turned. The English
fortune smiles is the same idiom in the same register, luck personified and turning its face toward you, and the two match idiom for idiom, which is the truest translation a phrase like this can have. On a wall it is a hope, and a good one to give. 運が向く is composed of the word
運 (read un) meaning "fortune; luck", the grammatical element
が (read ga) which indicates the previous word is the subject, and the verb
向く (read muku) meaning "to face towards".