As my dear friend Heartbang said, I think Nutuk is a good starting point for understanding how Atatürk's character and thinking evolved. It will give you a reflection of his ideas on specific topics, and therefore a reference on exactly which topics you should go backwards through these points of interest. It is an important work in terms of the history of the Republic, in which Atatürk narrates the War of Independence period in the first person. With the Nutuk, Atatürk describes the past and at the same time talks about the lessons to be learned in order to anticipate the dangers that may occur in the future.
It has been translated into many languages and you can find a copy at a very reasonable price, under $5. If you would like, I can provide you an English edition of the book as a gift.
I have no idea about the translation, but you can also find it as a pdf here:
https://archive.org/details/nutukmustafakemalataturkpdfdrive.com/page/n7/mode/2up
On a more personal level on Gazi Atatürk's life , there are many books, archival works and memoirs written about Atatürk. I and all my friends here would be happy to help you with any specific topics of interest. In any case, Nutuk is a must if you want to create an Atatürk area in your personal library. Also, as a complete narrative with biographical elements, I recommend the book Gazi Mustafa Kemal Atatürk by İlber Ortaylı, one of the most famous historians of our country, if you can find the English edition.