Whether the invitation says "festive cocktail," "festive formal" or "festive black tie," select the most showstopping version of the type of dress code "festive" is modifying
That way, if you really can't measure yourself, you don't have to." I chose a white classic shirt as it is a must have wardrobe piece that literally looks good with everything
As for purses, yellow or pink would be a fun choice (especially for a celebratory occasion) but you won't go wrong with silver or black
Bring a light jacket or shawl for cooler nights
If the dress is floor-length (or clearly cut as an evening gown), made in an elevated fabric with a polished finish, and styled with formal accessories like an evening clutch and intentional jewelry, it will typically read black tieespecially once you consider how it photographs in evening reception lighting.