Practice in the show style. each outfit is a reference to other characters the VAs have voiced.
 
edit: Twilight is Raven with nods to Batgirl and Ben 10, Sunset is Chelsea from Tokyo Underground (old anime), Fluttershy is X-23 from her very first appearance anywhere, Pinky is Andraia from Reboot (old CGI show), Rarity is Auriana from Lolirock, Starlight is Sango from Inuyasha, Trixie is Marie Kanker from Ed Edd n Eddy (though combining their hair didn’t really work), Rainbow is Mira from the Hollow, and Applejack is Mary Test from Johnny Test.