Replying to Semi-formal attire

alright so tomorrow night i'm going to an event that's "semi-formal" as so i was told. And since whenever i i have to go somewhere "formal" i just wear a wool business style suit that's blue with a orange/light blue tie. but this semi formal thing kinda threw me off so what exactly is it limited/unlimited to?
i have a black wool/silk suit that's less businessy so should i wear that? also black bow tie? white dress shirt, light blue dress shirt? or black with white striped dress shirt? maybe a watch? idk NS give me some combos that will look fly. for the record im about 5'8 145, light brown hair