If you are still not sure about what to wear to a cocktail party, do not fear! A general rule to follow when attending any party is to dress a little fancier than you would on a normal day. It is always better to be slightly overdressed. Finally, make sure that whatever you choose to wear is comfortable. And suits your body language and off course others too. Parties are all about mingling, eating and drinking, clicking pictures so feeling comfortable is important.
Most important please do not forget to hire a professional candid photographer to capture your cocktail party. The best way to make it memorable.