Navigating all the possibilities to find the most suitable attire at parties can often be overwhelming. Luckily dress codes are often clarified and choices can be narrowed down even further when we ask ourselves the relevant questions... A dress code is more or less a mandate to be followed if the function is formal and the host has specified formal attire. Think the black tie event, the wedding, the Bar Mitzvah. Conversely, the dress code may also be the theme. E.g. Hawaiian Shirt Next.
Why is everyone getting together? Dissecting the occasion will give you ideas. Engagement parties and those work related gatherings would speak an alternative look to a sweet 16 birthday. Then ask yourself where this party's being held...
The protocol is somewhat easier if it’s someone’s house. External factors such as the weather can influence your choice if your party is rooftop or garden themed. An indoor venue’s dress code could apply.
And finally. You’ll eventually be faced with no code whatsoever but a key calendar date. Halloween, Christmas. These, among others are often dress to impress events and are well catered for by the market for fancy dress.