What you've got to know is that Platinum is an oki and mixups based character with bad oki and unsafe but strong mixups. The first things you should learn to PLAY her are her normals, what's their max range, how well you can antiair with them, the spacing on antiairs, how good they are for meaties, how safe and unsafe they are, etc. Next thing I'd say is learn some BNBs so you can start getting some wins, and after that I say learn how to use Dream Sally or whatever it's called. If your opponent will respect your oki (because you conditioned them to) you can subject them to all kinds of baits and unreactable high-low mixups.
Main:Slayer, Kim, Ash, Nero Chaos, and last and least, Hakumen.
Takotoo: i want
Takotoo: a story about
Takotoo: hazama stealing my kokoro
Takotoo: fucking the shit out of my shota butt