" While often simulationist (in combat) and narrativist (elsewhere) to play to the respective strengths and game expectations of each, there are gamist underpinings to just make it work smoothly and in a streamlined way. Take a look at the feature/spell recovery model. " This does not look like any theory to me, just labels as stand-ins for actual meaning. But this statement nears closer to an explanation to what GNS Theory actually means then the many pages written on trying to explain what these labels mean and how they constitute an actual theory. When you speak of simulation you mean combat in the game and narrativist just means everything else you do in the game. Gamist is just a label for "the rules". Not really a theory, more of a color code for what kind of game you prefer. "Is their much combat, I don't like games with a lot of combat?" "Do I have to do all that silly voice acting? I just want to roll some dice." "Are the rules easy to learn? I don't want to learn something new, can't we just play DnD?"
So to answer the OP. Figure out what kind of game you like to play and play that. How to play better? Really just play as much as you can and think about it as much as you can. Roleplaying games are just thought experiments writ large, and thinking about your play, what makes it good, what makes it bad, can be done anytime you want. Action, reflection, action, reflection, rinse and repeat.