The #1 source for affordable clothes and accessories are the Humana-stores. They are comparable to Salvation Army or Goodwill (but they aren't as cheap). The biggest one I know is at the Frankfurter Tor 3. But those Humana-stores are everywhere in Berlin, e.g. also at the "Zoologischer Garten" and the "Alexanderplatz". I have to admit that I prefer to shop at the others as I find the one in Friedrichshain to be a bit expensive in comparison. Might be because of the area it's in. It is more like a second hand store for hipsters whereas the others are more an adress for those in need. And keep in mind that you have to pay cash.
If you want to read more about the Humana-store and 2nd hand shopping in Friedrichshain in general, you should read the post on the Outsapop-blog here.
Though prefer living in the municipality Wedding (Mitte north), I'd recommend going to Kreuzberg for 2nd hand shopping. There is a shop called Colors in Bergmannstraße 102 (in the rear building) with a wide variety of clothes and a section where you pay per pound (though I think that's limited to a few days per week). On the way from the metro station you also pass Checkpoint, they sell a mix of old and new goods (both stores at metro station "Meringdamm").
Furthermore I recommend Jumbo 2nd Hand (Wiener str. 63, near "Görlitzer Bahnhof") with their wide variety of shoes and my favorite store (and that's an insider, I guess): just two doors along is a small store which mostly sells shoes and bags but for a great price (mostly 10€ a pair) and the owner always puts a chocolate bar into the plastic bag which I think is so adorable. I found my favorite shoes there.
Now let's talk about the distric Berlin-Mitte: If you plan to check out the famous department store KaDeWe, you should also visit the vintage shop Garage (Ahornstr. 2, metro station "Wittenbergplatz"/"Nollendorfplatz") which isn't far away from it.
If you'd like to do more high end shopping, Made in Berlin is the store to go to (Neue Schönhauser Straße 19, S-Bahn-station "Hackischer Markt"). They sell a lot of vintage (German) designer clothes from companies like Escada or Joop.
And if high end stuff is your thing, you will probably visit the Friedrichstraße anyway, so why don't you stop at Made in Berlin- store (Friedrichstr. 114a, metro station "Oranienburger Tor")?! They even have a happy hour every wednesday from 10am-3pm with a 20% discount.
Then, if you happen to be in the northern district Wedding, check out the Mini-Kaufhaus-Meyer in the Amsterdamer Str. 12 (metro and interurban train station "Seestr"). It looks tiny on the outside but is stacked on the inside, it’s like a roofed flea marked and a great source for furniture and home decor. Also there's a Red Cross-charity shop near by at Seestr. 55.
And then there are the flea markets, the place to be on Sundays. The most popular amongst "hipsters" is at the Mauerpark in the district Prenzlauer Berg (metro station "Bernauer Str", you can’t miss it if you follow the masses), it’s also the biggest one I know. Not that popular ones (and therefore maybe a better source for reasonable priced beauties) are the flea market at the Boxhagener Platz (again the metro station "Frankfurter Tor") and the ones in Kreuzberg, though you should check that in the internet when you are here as some move from time to time.
The most popular amongst "regular" tourists is probably the one at the Straße des 17. Juni. They sell mostly antiquities and designer clothes (a few months ago there was always a rack of vintage Burberry coats there and I always debated with myself whether to buy one or not, but I’m not sure if it’s still there). But it’s the one all the tourists go to; therefore it’s mostly conterminously overpriced.
If you'd like to shop for fabric, I've got two adresses for you:
The biggest fabric store I know is Hueco-Stoffe at the metro station "Jungfernheide" (Lise-Meitner-Str. 7-9). They are a whole sale so they carry a wide variety and also sell big quantities. Everyone is welcomed, designer as well as hobby seamstress. They sell in two stores: an outlet and the regular fabric store, both on the second floor. Just be aware that they only open during work-week and on the first saturday of each month.
And then, again in the south of Berlin-Mitte is a farmer's market at the Maybachufer near metro station "Schönleinstraße" every tuesday and friday from 11 am till 6 pm where they also sell fabric mostly for 2€/meter.
But of cause you can find sewing-sections at some department-stores as well. KaDeWe has one called Idee Shop and if you happen to stumble upon a Karstadt-store, you can find fabric and notions in some of them, too.
There must be tons I missed, so check out this link of the tourist information Berlin. If you made it so far through the post and one day visit Berlin, keep money, a metro ticket and a map on hand, and you are good to go.
