When choosing cards, consider their base hit points, damage, and skills. However, a low HP and AP card with very good special skills may be useful. Always have a healer in your deck. Cards that have special skills that can be activated faster are always useful. Also consider cards that cause multiple damage or freeze the other cards. Look at the time required for each card to attack, indicated by the number in the bottom right corner. Try to use cards that can enter into battle sooner, even though the slower cards usually cause more damage.