This app was mentioned in 2 comments, with an average of 3.50 upvotes
All cheap places. Just check their events pages for what is coming up.
Edit: I forgot to mention Music Around is a good local music app that has many of the smaller gigs / concerts in Berlin. https://play.google.com/store/apps/details?id=de.berlitec.musicaround&hl=en_GB
Also look at the Music Szene facebook page for more small local stuff: https://www.facebook.com/MusicSzeneBerlin/
Music Around is a good local Berlin music app. https://play.google.com/store/apps/details?id=de.berlitec.musicaround&hl=en_GB