Jumping into the classics of philosophy can be difficult without guidance, and many of the best guides are more recent. Many of them were also not originally written in English, so you’ll need a reliable translation. I would recommend starting with an introductory book, which you might be able to find at your local library.
If you must begin with primary sources, however, try the early dialogues of Plato. The Apology and Euthyphro are excellent introductions themselves, and both are easy enough to follow. Don’t approach Republic until you have a feel for the dialogue format.
Alternatively, you could mix all three of your interests by reading Darwin’s Dangerous Idea by Daniel Dennett. The book is about the philosophy and science of evolution, as well as some of the sociopolitical reactions to it. Moreover, it is written to be accessible by general audiences despite being serious philosophy. Dennett is a controversial thinker, but the book is very well written. I would expect most libraries to have it.