I'm a daily practitioner of Stoicism, so I can recommend you a few things. It's a wonderful way to orientate your life. The foundational books (i.e. the ones that outline the basic tenants) I could recommend are:
Meditations by Marcus Aurelius (free on Project Gutenberg)
The Enchiridion and Discourses by Epictetus (my favorite, also found free on Project Gutenberg as 2 separate books)
Letters from a Stoic by Seneca (there are a lot of different letters he's written, which you can also find free online but they all have different titles)
For more modern applications of Stoicism:
How to be a Stoic by Massimo Pigliucci
Stoicism and the Art of Happiness by Donald Robertson
A Guide to the Good Life by William Irvine
And books by Stoics but not 100% Stoic:
The Subtle Art of Not Giving a Fuck by Mark Manson
The Obsticle is the Way by Ryan Holiday
There are 2 main websites where you can get some great info too:
Howtobeastoic.wordpress.com (By the Professor Massimo Pigluicci who wrote the book above)
Modernstoicism.com (By Proffesor Gregory Sadlet who has a great YouTuibe Channel about Stoicism and Philosophy)
DailyStoic.com (By Ryan Holiday, the author of the Obsticle is the way book above)