Berlin is very different. In West Berlin you have a "normal" German city and some areas with higher society and the normal shopping possibilities and brands (KaDeWe, Kurfürstendamm).
I would recommend to stay in "Mitte" or in the East ("Prenzlauer Berg" / "Friedrichshain") where you can find a very alternative scene and a lot of gastronomy. And it's great for shopping (independend brands and small stores). "Neukölln" and "Kreuzberg" are very interesting too, but even more multicultural and sometimes a bit distrubing.
Berlin is very cheap, also the Hotels. I normally stay in the area of the "Ostbahnhof" (train station east) or "Hackescher Markt"/"Alexanderplatz" (very central). There you can find great hotels for fair rates (for example Amani Hotels or "Intercity" where public transport is included in the room rate). Will be there for 55€ per night in July.
If you prefer budget, I can recommend "Days Inn Berlin City South" - you can get a single room starting at about 35-40€ including breakfast. It's in the middle of "Neukölln", right next to the subway. It's a deprived area of Berlin, but I never felt uncomfortable.