You can ascend your Sorcery Card to increase its max level. The first ascension costs coin but subsequent ascensions will require ascension materials. You can get these materials from the Oak of Deep Sorrow. There is a different arena for each Calling and you must acquire materials that match the calling of your Sorcery Card. The arena rotates each day so there is a different Calling arena for each day. Saturday and Sunday will have all the arenas available.