The only way to approach this subject systematically is to consider the history.
Start with Russell's History of Western Philosophy.
https://www.amazon.co.uk/History-Western-Philosophy-Routledge-Classics/dp/0415325056
It's short and covers quite a lot. For the bits that you get particularly interested in you can dip into, Russell's old sparing partner Copelstone. His history is somewhat longer at 11 volumes, but that can be bought separately and can also be read as PDFs.
https://en.wikipedia.org/wiki/A_History_of_Philosophy_(Copleston)
I believe the c way to study philosophy is to have a Question that you want answered and then do inquiry into all fields looking for answers. It is only through way that one can grasp the feeling of the philosophy. You have to walk the same path and not just read about the ending. It takes more time, but you get a much deeper understanding of nature and life.
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Start with Russell's History of Western Philosophy.
https://www.amazon.co.uk/History-Western-Philosophy-Routledge-Classics/dp/0415325056
It's short and covers quite a lot. For the bits that you get particularly interested in you can dip into, Russell's old sparing partner Copelstone. His history is somewhat longer at 11 volumes, but that can be bought separately and can also be read as PDFs.
https://en.wikipedia.org/wiki/A_History_of_Philosophy_(Copleston)