If you haven’t played Persona 3 FES, Persona 4 (Golden?), and Persona 5, you’re missing out
My personal recommendation would be, if you have a PS2, to buy and play Persona 3 FES, as it’s my favorite - but Persona 5 is amazing and the most accessible, so maybe play that first?
Or maybe wait until Persona 5: The Royal is released later this year? We don’t know when that is, or how good it’ll be, or if it’s DLC or a new game, so I’m hesitant to recommend waiting, but I also wouldn’t be surprised if, much like Persona 4 Golden, Persona 5 Royal becomes known as “the definitive edition” of the game.