Longchamp bags are amazing for travel! They can carry a lot and can also be folded. When I was traveling with cheap airlines, they have a restriction with carry on items and sometimes restrict you to one. You can easily fold your Longchamp and use it once you get to your destination. I have the Le Pliage Large Tote Bag in Black that I love and use all the time. It carries everything and matches all my outfits. In addition to that, I have the Le Pliage Large Travel Bag in Beige. These bags are a bit expensive but definitely worth splurging on because of their versatility and durance. You can go to the website here http://us.longchamp.com or go to an outlet store for a discounted price on bags.
People still argue that leggings can't be pants but if worn with the right top then I think leggings are definitely acceptable. Sometimes you will walk and travel for hours on hours abroad and you'll want to be comfortable. I highly recommend leggings because they can keep you warm when you go into a cold museum but still feel light when you're out walking in the sun. My favorite pair of leggings is from fabletics.com.
A great shoe to walk around are white converse. They're lightweight yet give you the support to walk around all day. Sneakers can also be worn for walking around all day but if you're looking for something a little more fashionable then I would definitely recommend white converse. You can get cheap converse type shoes from so many different stores. I have a pair of white ones from Target and only cost about $12. Therefore, if you get them ruined then not a big deal because you can buy another cheap pair at another store. So you really have two options: converse or knock offs. Either way they're great to walk and explore your destination!
If you're traveling somewhere cold, obviously you'll have a thicker jacket. If you're traveling somewhere hot, obviously you'll have no jacket. But, if you're going somewhere in between, then a cargo jacket is perfect. Mine is from Forever 21 and I like it because it can easily be folded up and put in my Longchamp or I can carry it without getting tired. They're perfect for the in-between weather so you can leave it on or take it off.