So you've picked a setting for your movie that could offer many possibilities. Have you any theme, plot, characters, etc. in mind, or is that up to the Writer? I can envision different takes: action, satire, neo-noir, comedy; heck, in too many places in the world it could be a documentary. Are you thinking short or feature? And you say you want to make it yourself; have you a budget level in mind? A smaller budget suggests a more cerebral piece, more mindfuck and less reliant on huge setpieces and special effects.
Two story premises that immediately suggest themselves to me come from your "transformed into a police state". That transformation is inherently high stakes!
This could be the story of the transformation; perhaps the dominant political party has been plotting this coup against the citizens for years, and the movie is the final battle between the totalitarians and the people who recognize what's coming. Maybe they feel helpless to prevent it, in the face of general public indifference. Maybe they uncover a deliberate plot for some crisis that causes the scared populace to embrace the totalitarians; that's maybe a paranoid political thriller. In fact, what if the hero is a conspiracy theorist who discovers that the truth is even worse than their worst fears? And they can't get anyone to believe them! You could have a downer ending, where the party succeeds in imposing its totalitarianism, or an up ending where our heroes successfully overcome the immediate threat and awaken the citizens to the danger -- but the danger always remains, and the price of freedom is eternal vigilance, and blah blah!
Or this could be the story of the counter-transformation -- the struggle against the totalitarian political party by dissenters. In this world, the party has already established its rule and stifles dissent, and our heroes are rebels against the enforced conformity. Perhaps they're independent journalists, somehow managing to publish dissenting material about what's really going on that you don't see in the government-controlled media; "journalists crusading for the truth" has a long history, and you could make it a thriller or a satire. Or maybe our heroes are a violent, sadistic street gang, and the theme asks whether we'd rather have enforced peace or violent freedom; then you've got a social satire. Again, you could have a downer ending where the party crushes our heroes, leaving us feeling that resistance is futile; or maybe they make a heroic sacrifice that ensures freedom for everyone at the cost of their own life. Or you could have an up ending, where the resistance succeeds, the party is overthrown, freedom is restored, and everyone gets cake!
I'm sure there are other, more original ideas to be had; this is just off the top of my head. But the more specific you can be about the kind of script you're looking for, the better able people are to help you.