In September I will be in Berlin, Prague, Vienna and Budapest. Trying to figure out type of clothes I should pack (more summer attire or fall). Thinking jeans and a t-shirt for most days. However, Vienna and Budapest seems a little nicer. For the evenings Long sleeve dress, leggings or a skort or linen pants? Thinking Vessi sneakers, Keens sandals and Teva sandals or Vessi shoes and flats. Depending on the airline I may be only allowed to under 13 pounds for my carry on.
Instead of t-shirts, bring blouses. They are lighter and dressier. With long sleeves, you can roll them up if it gets hot. Toss on a dress jacket and a light scarf and you will look perfect every where.
I think it depends on your tee shirt! I have shaped tees from Lands End that are a cotton/modal blend that are a bit nicer than a standard 100% cotton Tee. I just bought 2 tee shirts on Friday at Macy's that are the Ideology brand of athletic wear that are purported to be quick dry. They are lighter weight than the Lands End tees (yes, I weighed them for comparison). I will see how they do before I travel as in the past some of the athletic wear gear has held in BO....so even when I didn't smell the shirt did. I won't take a tee that I can't wear multiple days before washing. They look dressier than many athletic or regular tee shirts and have a slight texture to them. They don't really have an athletic cut.
I'd plan to layer - SS Tee shirt with the option of a LS layer. I use a LS quarter-zip dri-fit as they are light yet can provide warmth especially under a waterproof rain jacket. On some trips I've taken a cardigan but they are so bulky that you really have to wear it on the plane and on every transfer. It does look dressier than the quarter zip.
I've been to Vienna and wore my same capsule wardrobe. I did not go to any concerts, however. Are you planning on evening events? That might be the only reason I would take something other than your regular travel pants which might be jeans or leggings. Are your jeans a combo fabric? Mine are Gloria Vanderbilt Amanda jeans which usually are a poly-cotton blend which dries faster. I'd take either one dress or 1 pr linen pants if they will be your dressy outfit for something special. I would not take a skort. Leggings only if they are multifunctional.
I have not been to Budapest.
Unless you are considering fancy restaurants or concerts, I'd keep with your same travel basics. I do not think you need to "dress up" for touring a city.
13# is pretty light. I got my suitcase down to 16.1 last fall for 3+ weeks in Italy but only because I weighed every single item I put in AND got the lightest weight suitcase I could find at 4.5#. How much does your suitcase weigh?
September in Vienna is still hot.
We were in Vienna in the middle of Oct 2019 and it was still quite warm. My strategy is to pack some short sleeve and some long sleeve and buy some souvenir t-shirts in either sleeve length if the weather requires it. I also pack silk long underwear-it weighs almost nothing and takes up little space in your luggage and under your clothes, and will dry relatively fast after being sink washed. Also leggings can be a layer under slacks if necessary.
I pack exactly what I wear in NYC in September. Black cotton 3/4 sleeve blouses, merino cardigan, black leggings both lined and unlined since they are very lightweight to carry, undies, knee high black socks, pashmina scarf, leather gloves, 1 or 2 silk scarves, walking shoes, compact rain coat, collapsible umbrella, nightie, flip flops, bathing suit. I also bring a couple of sleeveless blouses in case there is a heat wave. I wear waterproof boots to travel since they are heavy. I make sure my Pullman suitcase, which is my carry-on, weighs no more than 10 pounds. That’s all I can manage on my own.