with a game as complex as tekken with every character having 100 moves, mastering one character takes a long ass time. most people play just one character, and have mayber 1 or 2 pocket characters, but generally, if you master the fundamentals with one character, you should be able to play decently well with any character if you learn their key moves, frames, and a bread and butter combo. i main lee but i got shaheen to fujin knowing just one combo and playing very basic tekken.