I have played this game in different ways in different periods in the past, as a small buyer, as a medium buyer, as a big buyer but also as someone that did not buy anything and could not even farm green packs as there were no offers (played on browser platform only during a period).
Way back it was possible to play this game comfortably and be competitive without spending any money, but things have changed with time. Only those that have saved resources from many seasons can do this those days; someone new to the game or back to the game after a long period of absence, that is those with not much resources in their game accounts will have a hard time soon or later to stay competitive in all the competitions as they get promoted every season because of the new market system and the amount of tokens and green packs other users have in stock which they can afford to splash them here and there. SuperDunk and others users that recently came back to the game with little resources on their accounts can tell you more.
Also, players have become harder to keep to a certain level of quality season after season because of the new limiting system for the progress of individual attributes; this game has become even more of a buy, use 1-2 seasons and dipose thing.