
You're going to (fill in the blank -- Costa Rica, a beach in Delaware, the
house in Newport or ...) You have a finite amount of space (not to mention,
often, the headache of packing children and even the significant other). What
are you going to take?
The answer, of course, depends on the length of
the trip -- but not solely. (A house has laundry facilities, of course, but so
do most hotels).
You'll need one basic -- whatever you can dress up,
dress down, wear sightseeing, to dinner, for ice cream on the boardwalk over
your bathing suit. A knee-length cotton-lycra skirt in a neutral like olive,
khaki or ivory would be perfect.
Next, several tops, maybe three or
four, also in lightweight knit neutrals.
Then add a dress or
tunic. Here's one by Sweet Pea, which I'm a huge fan of, and everything they
make dries extremely quickly, which makes it perfect for travel.
Include
a pair of lightweight dressy jeans, which you can pair with one of the tops or
the tunic. (The dress or tunic should be one that can also be worn by
itself.)
Sweet Pea Empire Waist Tunic Top ($86)Add a third "bottom" -- a pair of longish shorts, for instance, or another skirt.
And that's your basic travel wardrobe. You can add to it, if you want. (Just remember the general rule of travel: most people pack way too much.)
Now, here's the hard part. I am a firm believer in packing the extras that will give your look

punch while you're traveling -- the accessories that can help you transform your beach look into dinner attire without breaking your stride.
So: You'll need a very lightweight cashmere shawl, preferably in a neutral color (yep, just like they tell you once a year in Vogue magazine). (A cotton or silk pareo would also do double-duty as a wrap or shawl.) Some dangly, night-time earrings. A versatile pair of heels. Some throw-on jewelry (like necklaces or chains to layer).
Diagonal Ombre Scarf by Yarnz ($105 on sale) 
A vest or a tank top or something else lightweight and whimsical -- maybe a silk camisole -- to help you get extra mileage from your basics.
Graham and Spencer Metallic Swing Cami ($208) Add a couple bathing suits and flip-flops and you're all set. No one will suspect you're a tourist!