Refinery29 Reserve has deals for Bird and Eaton Trading Co right now. There's some overlap in designers, so depending on what you want to get, you might save more going with ETC ($150 for $300) or Bird ($100 for $200).
I'm leaning toward the APC linen drawstring dress at ETC, but I'm also in need of a simple pair of sandals that can work with a dress. Has anyone tried Ancient Greek Sandals? I usually don't wear heels or wedges, but this one looks doable.