It depends on what you want. Do you want Western Philosophy or Eastern Philosophy?
You have the basics of Western Philosophy like Plato, Socrates or Friedrich Nietzsche.
Eastern Philosophy, you have Buddha, Rumi, Confucius, and Laozi.
There aren't really any texts from Socrates though, it's more about his life written in a perspective from another man. Plato writes a couple about the man's life. It's pretty good, I guess. I'm not a fan of Western philosophy other than Friedrich Nietzsche, unfortunately.
Friedrich Nietzsche wrote "The Gay Science" and a couple other books. He was the one that coined the term, "God is Dead."
Buddha is Buddha. You know the nigga.
Rumi wrote a lot of religious texts, based mainly around the Quran. He writes a lot of "cycle of life" bull, except it's surrounded around the Muslim God. He's pretty good though.
Confucius says a lot of things. There's a reason why there's an entire religion surrounded around him.
Laozi was the contrast of Confucius. He was the one who said "Without Darkness, there can be no Light."