Get dressed right for traveling
It is very important to have comfortable and functional clothing for traveling. Because you're not at home and don't always have the opportunity to change.
You don't need more than one trusted go-to outfit, but it should be right, to make your life simple so you wouldn't have to think about anything else than enjoying your trip.
So, here's an idea:
A buttoned-down shirt or a black T-Shirt. It's simple, it combines with everything, and it's easy.
Pants. They need to be soft and comfortable, but not look like pajama pants. They should allow high mobility and sitting in the most inappropriate places, so choose a darker color.
Jacket. It should be comfortable, it should look good and, ideally, it should be waterproof. Also, it should match with almost anything, so choose a between-styles one.
Scarf. Very useful. Use it when you're cold, as a pillow, as an eye-mask, as an emergency tie or anything your creativity allows.
Shoes. What we want is comfort, so no huge heels. They also should have zippers, so you could take them on and off easily whenever you need. Stay away from open-toe shoes, they may cause inconveniences you'll never think of until they actually happen, like when you drop a suitcase on your unprotected toes. Or when you have to run to catch a connecting flight or train or bus. Or when your feet get cold on the plane.