On a leafy street in Kreuzberg is Kuratiert, a contemporary illustration gallery and shop selling prints, ceramics, textiles and more by some of the best creators from Berlin and the world. It also hosts regular dedicated exhibitions, and is a great place to browse for gifts, or just inspiration.
Kw is a great art institute situated at the backyard of a very eastern part of town, place for many other small galleries. Auguststrasse is worth the walk and Kw is worth the stop.
A very nice little second-hand bookstore, including a shelve with international books in French, English, and Spanish too. Always nice people to meet and a great selection of art and cook books, for affordable prices.