I'd suggest Adam Smith and Marx were terrible starting points tbh, since both were writing long before anything resembling the theories and methods of modern economics - or actual modern economies - actually existed and the one thing they had in common (a labour theory of value, though Marx's is more sophisticated and fundamental to his theories) is something essentially no modern economist believes. Not that they're not interesting reads and influential on what came after, but it's like trying to get a grounding in computer science from reading Ada Lovelace.
Arguably even the bad theories are better understood in the context of modern economics (Marx's "Iron Law of Wages" which proposes that wages inevitably fall to subsistence levels makes much more sense as a special case of there being more supply than demand for that type of labour; one prevalent in the middle of an Industrial Revolution which made many craftsmen obsolete but less evidently a universal truth after a century of most people in the West earning well above the minimum necessary to keep them alive)_
Arguably even the bad theories are better understood in the context of modern economics (Marx's "Iron Law of Wages" which proposes that wages inevitably fall to subsistence levels makes much more sense as a special case of there being more supply than demand for that type of labour; one prevalent in the middle of an Industrial Revolution which made many craftsmen obsolete but less evidently a universal truth after a century of most people in the West earning well above the minimum necessary to keep them alive)_