Very smart idea to travel light. I visited Italy in April and wore the same few outfits over and over again. I washed and hung my clothes out to dry (used Woolite travel pack detergent).Bring what you are comfortable in and feel cool in. ***No shorts!*** They will not let you in the beautiful and historic churches, and shoulders must be covered. You can definitely wear tank tops, but bring a scarf to cover your shoulders in the churches. Actually, some people do the same and wrap it around their waists to cover their knees so that is another option for you.
My suggestions are: knee length skirts, cropped pants, tanks/ light tops, scarf, powder (it is hot!) and antifungal cream for your feet (again, hot sweaty!). Comfy shoes with suppport. I wore flats one day, but never again because the cobblestone streets take their toll on your feet and ankles. No need to bring an umbrella if space is an issue and you are in a major city. I was in Rome, Florence, and Assisi and vendors come out of the woodwork to sell them. In Roma, you can buy one for 2 or 3 euros; the price is negotiable there. It rained almost every day I was there. Hope this helps! Alison