I wrote a long reply yesterday, but for some reason, the forums do not let me be the first to answer. So it was lost.
Personally, I hate traveling in jeans. They're too hot for summer, too cold for winter, and they (along with other thick cotton) take forEVER to air dry. I like to bring things that I can wash in the sink, hang dry, and be ready to wear the next day. For summer, linen is indispensable.
I also find my cashmere cardigans to be useful against breezes, over-zealous air conditioning, and general warmth. Layering is the key.
You know those plastic bags you get at the dry cleaner? If you wrap your clothes in that, they won't wrinkle.
I find skirts far more versatile than dresses.
Stick to one color scheme.
If you plan on visiting religious institutions, make sure to have your shoulders and knees covered.
For point of reference, I spent two months abroad with nothing more than a carry-on and was dressed for all occasions, including fancy dinners along the Riviera (I wrapped my silk gowns in the plastic dry-cleaner's bag.)