This is for you, Rita. There's a lot to cover so to make it easier I've split it into the sections according to the old Chinese way with an addition: 衣食住行 （clothing, food, accommodations, transportation) + packing and stuff.
Bring clothes that can be easily layered and washed. More likely than not you will not have a washing machine or dryer and the cost will add up if you are having to do coin laundry. Look for fabrics with natural fibres (such as silk, merino, cashmere, viscose). Quality fabrics will fare better after many washes. Don't worry about the dry clean only tag, 90% of the time hand washing with a delicate detergent in cold water works just as fine. Example: for a 100% cashmere sweater; rinse, squeeze out water (do not wring), lay on top of a dry towel and roll up. Leave for 15 minutes or so and then unroll. It should be almost dry so all that is left is to lay it out on another dry towel to dry overnight.
If you will be traveling through different seasonal temperatures, look for pieces that are flexible. E.g. a nice floral dress that you can wear with sandals in warm temperatures and then pair with a t-shirt, tights and boots for cold weather.
Bring neutral accessories which can be used with more than half of the clothes you bring. Do not bring your sparkly chandelier earrings (even if you think it is the best of all your jewelery) if it only goes well with one thing.
Scarves are also great for accessorizing and keeping warm.
Bring shoes that you can walk in for hours. They should have at least 1/4" sole to save your feet from the damn cobblestones. Unless you really really need heels, I say keep them at home and save the luggage space. Flats will work fine in 99% of the situations that you will incur. The remaining 1% is if you get a hot date or have an opportunity to walk the red carpet.
The above being said, keep your pieces stylish, ie. should not be ugly or else you will come to regret it in the years to follow whenever you see your Europe pictures. People in Europe are probably still talking about my neon pink bomber jacket.
Good safe colors that will carry you all over Europe (especially France): black, navy, khaki green, beige, red.
a good, warm black coat
waterproof trench or pretty raincoat
plain t's with long sleeves and short sleeves
pair of solid color jeans (no stone washed)
ribbed tank tops
straight or skinny dress pants
a nice top (silk, chiffon, jersey)
pair of sturdy black boots
classic ballet flats