Without seeing your dress and glittery, gunmetal sandals, it is difficult to know. Because of the beading glittery sandals might be too much. You can do a mirror test to see how the outfit looks then decide. Try some silver jewelry to pull the look together and a plain black bag. Black shoes sound like a better choice. You can wear a black beaded handbag that will pick up the black beading on your dress.
Buy footwear in mid-afternoon when your feet are at their largest. Choose a style which suits your foot shape (do not force your feet into ill-fitting shoes). Be sure to allow some space between the end of your longest toe and the end of the shoe and ensure that the width fitting is correct. When buying shoes don’t expect tight shoes to loosen up.