Buying textbooks when studying a Master's in Germany?

I already feel like, this is a stupid question and I'm gonna get roasted for it :D

In a few months, I'd start a Master's degree in German in a public university in Germany (subject: BWL). I'm just wondering, should I buy the original textbooks for each course? On the one hand, I want to get the best marks in each course and learn the most. On the other hand, I can imagine, it's gonna be expensive.

How do German themselves go about this?