Something I wrote from an online discussion group in which I am participating, about Philosophy and the Question of Evil:
The philosophical/theological subject of why evil exists is called theodicy. It presumes the existence of a benevolent Supreme Being, and asks why the Supreme Being, if benevolent, allows evil to exist. Most theodicies are religion-specific. As a Jew, I'm aware of Jewish theodicy, which because of the Holocaust has become very central to Judaism. The book of Job in the Bible is a very old explanation of theodicy, but I'm not sure its conclusions are very satisfying to everyone. I prefer the theodicy of the book of Jonah. Evil has to be confronted, but people have free will to abandon evil and seek to do good. The king of Nineveh repents of his sins and encourages the whole city to repent, and they do. If you think it happens too easily, consider the journey that Jonah has to make to bring his message to Nineveh.
My personal theodicy is that evil is an inherent by-product of being separated from the One. I'm not separated from the One, but my ego thinks it has an independent existence, and from its perspective, it does to some degree. In three dimensions, my body is not connected to anything larger, but in more dimensions, that ceases to be the case. To the extent that I can find my way back to where I am connected to the One, I retreat from evil. To the extent that societies can find their way back to where they are connected to the One, they retreat from evil.
But I exist in a world of some complexity, and there are a lot of moving pieces that aren't me in my current perspective. Sometimes those moving pieces cause chaos and havoc and destruction, either through human agency or through natural forces, and evil is the result. Evil changes with perspective. It does not have permanency, although it seems to have ubiquity.
That's only my opinion, and very much flavored with my religious convictions. Jesus as a Divine actor in this reality makes the dynamics of Christian theodicy quite different, and Muslim, Buddhist, Sikh, Hindu and ancient Greek theodicies all have their own individual flavors.
But pure philosophy, separated from faith, cannot handle theodicy, as far as I'm aware. Without the idea of a benevolent and loving Supreme Being, there'd be no reason why evil wouldn't exist.
My experiences with philosophy, while enriching, have not been especially grounding. A spiritual practice, especially one in the body, seems to ground me more than philosophy does. Walking without talking, or sitting in meditation or prayer, or martial arts study have been very grounding for me. Exercise in general helps, especially exercise in silence. Mathematics stills my mind as well, especially geometry. The three-volume Dover paperback of Euclid's Elements is a great place to start. Get a ruler, a compass and actually construct the geometric constructions along with the book. The Dover version is annotated by Sir Thomas Heath, who is brilliant. You can get lost in his footnotes. Don't get lost, but enjoy them. Working with a study partner or partner helps.
Philosophy for me begins with Plato's dialogues. Plato is not always right, but he hits all his marks. I would start with the Republic, which is an exploration of Justice. If you can, read it with a friend or with many friends, and get together regularly to discuss it. It is not an accident that Plato's Academy had a geometry pre-requisite.