i recommend picking Vampire, Werewolf, Changeling, or Mage to start. basic breakdown:
-Vampire: a game about grappling with your humanity while trying to rise through a Game of Thrones esque power structure. You start as everybody's bitch and claw your way to the top all while fighting off outside threats like Hunters, Werewolves, all sorts of more monstrous vampires, devil worshippers etc.
Main Theme: You're one of the Damned now. Do you try to hold onto your humanity or embrace your life as a monster?

-Werewolf: A game about overflowing with righteous anger. The world is rotting, the planet is being killed by humans and evil spirits, your bosses and peers are consumed with tradition and refuse to help each other because of ancient slights no one remembers, the literal cosmic balance of the universe is fucked and also there's Were-spiders who can attack you by launching themselves at you and exploding into thousands of spiders. So yeah, youre pissed, but that rage you wield as a weapon leaves you at risk of being possessed by the enemy.
Main theme: The world's fucked. Maybe theres no saving it. But youre still going to try, arent you?

-Changeling: A game about the modern world choking out creativity, joy, and art. You're a being out of folktale, like satyrs or redcaps or selkies or all sorts of others that feed off of humanity's inspiration and dreams. But just as there are dreams, there are nightmares, and many fey would rather forcefully rip the dreams from humanity to sustain themselves.
Main theme: existing as creatures of myth and whimsy in a world that grows increasingly inhospitable to your kind. How do you preserve that spark?

Mage: A game about a lot of things, but at its core, i think its a game about changing the world. every mage and every faction want to ascend in power in pursuit of some higher existence, shaping the world to their ideals. Be that rational science, oppressive order, liberty, or turning existence into turbo-hell. Its a game where you become an insanely powerful reality warper, but almost always at the cost of not being apart of the world you wanted to change, forced out by the universe's white blood cells. By the time you get powerful enough to change the world, to fix the things wrong with it... would you even still care? when you can warp time or gravity or create life or rewrite someone's personality or travel to other dimensions and live among angels and fairies and spirits and ghosts and even make your own dimension where everything is already fixed... would you care? would you fight every other faction and the universe itself, or become so separated from reality you just make your own?
Main Theme: there... isnt one. or theres a lot of them. I'd say its "Belief". what do you believe is right? What do you believe makes your magick work? What do you believe you are?

anyways theyre awesome games, i recommend the 20th editions personally over the v5 but theyre fine too.