Get a few different translations of "Meditations". I recommend the ones by Gregory Hays, Martin Hammond and Robin Hard. The book is basically a collection of thoughts on various aspects of cultivating one's character and developing a "stoic" approach to whatever life may throw at you. It has no overarching framework/grand theory and thus you can read the individual thoughts in random order as the mood strikes you. It is quite practical and needs to be practiced in everyday life (with some commonsense changes to adapt to current time period).

You might also want to look into the works of Epictetus, Seneca and Cicero.