"Discrete mathematics" is rather a buzzword containing the basics of a dozen different topics (logic, algorithms, calculation theory, number theory, digital design, etc.), all of them are slightly related to programming. Reading a separate book in mathematics will be about the same as reading the first or two books on all of these topics.
The most important thing to understand is logical logic , which you are probably already very good if you are self-taught; algorithms are also very important. The theory of computational materials is quite interesting, but not very useful if you really do not use algorithms or do not want to write your own parser. Number theory is good to find out if you want to break into cryptography.
You do not need to know any of these things to read about data structures.