If you have only seen the Magic Card Shisakura on TV, you can start from the ending of the Magic Card Shisakura because the ending of the Magic Card Shisakura is the ending of the TV series and animation version, not the ending of the novel. If you want to start from the original novel, you can start from the first season because the first season of the original novel mainly tells the story of the school life of the magic card girl Sakura, the first card draw, the magic teacher and the story of finding the little Cocker Boy. If you want to know more about the story of Mokka Shūsakura, you can start reading other chapters of Mokka Shūsakura's original novel.