I recommend Seneca’s moral letters. Easy to read, copious analogies to support his conclusions, 90% of it deals with practical living, and did I say, easy to read?
Some things I have learned about philosophy.
1) Greek philosophy was equivalent to the modern university. People would go to philosophic academies to learn about various things just as today they go to earn a degree in various subjects: physical sciences, ethics, medicine, politics, mathematics, etc. Therefore, philosophy in Hellenistic times meant then what today means, to be educated.
2) Greek philosophy originated in a revolt against the traditional Greek religion, although, was the greatest promoter of a unified impersonal deity or source of all things characterized as a thinking and absolute Good deity. For this reason, some philosophers were characterized as atheists merely because they rejected the traditional superstitions of the Greek religion. Therefore, Greek philosophy parallels critical thinking today which rejects superstitions held by modern religions. For example, the science today supporting evolution absolutely refutes the literal interpretation of the Biblical creation myths resulting in critical thinkers today either rejecting religion altogether (militant atheists) or seeking a meaning that reconciles with the scientific truths we discover (theistic scientists).
The point is that the rise of science and critical thought TODAY all happened BEFORE in Hellenistic times aka, philosophy. IOW, history repeating itself. If so, then will formal Christianity (based on superstitious and supernatural anthropomorphic divine entity) be replaced by a modern theistic conception of a universal providence in harmony with science, —just as superstitious paganism was replaced by philosophic conceptions of a single intelligent cause of the universe? One can only hope, right?
3) Philosophy suffered its own form of internal corruption when some individuals used the knowledge of rhetoric and education to mislead others, usually, connected with politics. The good philosophers condemned the bad use of philosophy for personal gain. The bad philosophers gave the good ones a bad name.