You covered a lot of ground hopping countries. Give us some of your personal food/drink recommends from each city:
Paris Du Pain et des Idées for anything bread, Chez Prune if you want to dive head first into cafe culture (they have wifi), and Monoprix for absolutely anything you could possibly need.
Barcelona Bar Marsella for absinthe, Casa Almirall for vermouth, and Espai Joliu for an aesthetically pleasing coffee spot, not for from the beach in Poblenou.
Any souvenirs? I returned home with only two small things from abroad, both purchased in in Barcelona. 1) a tote bag from the Montana Colors flagship store and 2) a vintage Catalonian flag pin purchased from a vender at the flea market in front of the Cathedral of Barcelona.
You're often dressed in functional head-to-toe black when you're at the shop. What did you pack/wear when you were living out of suitcase for a month?
I think the most important thing is comfort. The best way to see a city is to walk, so from head to toe be as comfortable as you possibly can. And don't wear shorts in Paris.
You're traveling.. it's not a fashion show. And never will I say to not look good while doing anything, but you're going to sweat, you're going to get dirty, you might even get paint on yourself.... Minimalism with style. Choose pieces you don't mind sacrificing, as hard as it may be to decide which those will be. Your sneakers, if not already thrashed, they will be. Embrace it.
We have this perception of how people dress abroad, fed to us by the media and the Internet. While some of it is real, most of it is not; and what I mean by that is what you see are often looks put together by stylists and companies and shot to appear as if that's what people are wearing in order to sell you and me clothing and accessories. What we digest online is often exaggerated "street style" that very few people actually rock on the day to day.
People in bigger cities definitely have a style you don't see anywhere else, they just make it look effortless by keeping it simple.
What I wore for the majority of my trip was a Levis blue denim jacket (fairly washed, the inside pockets were a major selling point for me), dark colored t-shirts (most often black), black Levis skinny jeans, white crew socks and my white Reebok Club C 85s (very comfortable.) Luckily, I also packed a North Face jacket for those cold, rainy days in Paris when it got down to the low 40s (I almost didn't bring it so be prepared for situations like that.)