There is nothing more feminine than a simple strap dress. Combine it with heels and it becomes the best evening outfit. While black strap dress is always the best choice when in doubt, I am all into pastel/neutral colors lately and chose this Willa Dress from Dona Mizani (which is now on sale here http://shopstyle.it/l/y1QM :( right after I bought it) as my birthday outfit. It was love from the first sight: the material is very soft, straps are adjustable and the front slit allows movement and makes it very comfortable. I also love wearing pastel colors when I'm tanned so looking forward to warmer days! Strap dress itself looks chic so it doesn't require lots of accessories. I chose medium hoops and a chocker with my name-necklace as they look simple, yet chic with the dress and express my style.
Soft pink or black heels would both look good, but I chose black heels with gold details to match my jewelry and Furla bag (similar here).