This was like Scorsese saying....
......You ought to know the history of America to enjoy this movie even if you are not an American. Yes, I assume that you are already aware about Osage Nation and Osage and such unholy land where a bunch of White European Ethnics who married Red Indian Girls or 'married into' the oil land and moving around with English speaking Red Indian Wives (btw, sometime back I myself didn't have a clue about Osage). And I don't care to give any back-story or a narrative which explains this part of American history and while I know some of you (especially young generations) will have your face into 'WTF is going on!!' mode, I don't care! Eat this movie the way I present you.
I already did this thing with 'The Irishman' where the movie goes randomly in any direction where I want without giving any background of how Labour in US is controlled and the constitution of Union and its leaders and how politicians and mafias get involved; I like to feed a Mix contrived bag and make you land in a story wherein you already know who's who and what's going on. Very much Unapologetically.
Go and read Wikipedia extensively, run google; dump the history in your head, start the movie; pause whenever you get stuck; refer the net again; get your facts right and then make the sense out of this film. This is how you enjoy my movies! Good luck! Afterall my name, Leonardo Dicaprio & the glossy marketing itself will induce an inferiority complex in you and will dig...dig...dig.....and finally make sense of the movie.