Most of the summer weddings I've attended in the past featured an outdoor ceremony with an indoor reception. I kept the possibility of temperature variances in mind when selecting an appropriate outfit as a guest.
Outdoor ceremonies could very well occur on a hot and humid day, so I tend to favor dresses in lighter colors or ones with breathable fabric (or both). For this challenge, I went with the latter, a dark-colored dress in silk. The dress isn't clingy and flows nicely as I move -- great for dancing the night away.
The dress is on the casual side, so I dressed it up through accessories and strappy sandals. There's something about metallics that just scream "fancy" to me (shiny objects = bling, lol). I also brought along a shawl in case temperatures cool by nightfall. Ideally I would've preferred one with a nicer fabric, but I worked with what I had in my closet and loved the lilac pairing with navy.
I didn't even come close under the $100 mark for the outfit. If I exclude shoes and accessories, then yes, I'm under (but that would mean I cheated because the only item left is the dress). The cost breakdown for my outfit:
$9 Forever 21 gypsy necklace (similar)
$6 H&M gold leaf cuff (similar)
$27 Banana Republic solid jersey wrap (similar)
$66 Lauren by Ralph Lauren Aela shoes (similar)