Best bet might be to choose a location for a game, and then check to see if the team has a website for season ticket holders selling back individual tickets. As an example, the link below is to FC Bayern's marketplace.
I went to a Bundesliga game at Signal Iduna 3-4 years ago when BVB hosted Werder Bremen. Dortmund was not as successful then as they have been recently, but I was able to buy a single ticket online from the team website and print it on my computer two weeks in advance or so. With their recent form, I don't know if that is still possible. I went to a Friday night game and had driven from a plant site outside Hannover that afternoon. Traffic was ridiculous getting into the city for the game, so I parked about 2 km away and hoofed it in and just made it for kick-off. It was a great experience.