But, if you skip the dress and heels, the options open up. Plus, you don't have to worry about showing up wearing the same dress as someone else. The one downside to a dress is that it is very obvious when someone is wearing the same one as you. Skirts are great because even if someone else shows up wearing the same one, it is unlikely that they will have paired the same top with it. (Unless you both bought the outfit off a mannequin at the same store.) Your unique styling will keep you looking fresh.
For the top, choose a fabric with some sheen to make it feel formal enough for evening. I am partial to a silk cowl neck shell in a neutral color that you will be able to pair with a variety of bottoms. For the skirt, texture is key to making it feel dressy. Lace and jacquard are both great options that won't make you look like you ran to the ceremony straight from work. I love the cheerfulness of the orange and pink dot jacquard skirt from Boden, but for those less adventurous with color, there are some lovely black lace options from Ann Taylor and J. Crew.
My last suggestion for an unconventional wedding outfit is probably going to be the one that gets the most push-back because it goes furthest away from the wedding formula we are used to. Instead of a dress or a skirt, wear a pair of fancy pants. A straight-leg, ankle-length pant in a jacquard is a great option and can be found in the fancy pants section of a department store. Banana Republic and J. Crew also often carry jacquard ankle pants. Metallic accents, even if it is just metallic threads sewn into the pattern, and rich jewel tones elevate the pants to evening. Pair with a silk cowl neck top, a dark jacket, and heels. (I know I just tried to convince you to wear flats in the last couple paragraphs, but for a dressier event, an ankle pant should be paired with a heel.) A quick note on the jacket--get a jacket or blazer specifically designed for evening. The jacket from your business suit will have the wrong proportions and detailing for the formality of a social evening event. A crepe blend is usually a good bet and details such as gathering around the waist, a grosgrain ribbon tie, or a scalloped collar can make a black blazer the most wonderful piece in your wardrobe.
For more wedding related fashion thoughts, check out the wedding season tag and be sure to leave your questions and opinions in the comments! Cheers to many happy and stylish weddings ahead!