Ok so something to make people play with all there cards. Gizmo calls it The Kingdoms Army. To prepare your army for upcoming battles to protect the realm each troop in a kingdom gets a small buff and maybe even a Elite soldier or rank on the card in one of the corners. This is in no way intended to make troops op or give kingdoms huge buffs but rather a gratifying experience for ranking troops. Example
Kingdom A has 8 troops
When you win 50 pvp/explore battles with a given troop that troop gains 1 stat point to either health or armor and gets elite status or veteren status
Once you get 4 of the troops to 50 wins you get a 2 percent increase to tribute chance/amount/or gold
Once you get 8 troops to 50 wins you get 3 percent increase to tribute chance/amount/or gold
and at twelve 2 percent more
at sixteen 3 percent more and so on.
When you have all troops at any time all at 50 wins or more you get a marking on your kingdom that shows it is full of elite/veteren troops and when a new troop is released for that kingdom you lose this visual only buff till you win 50 games with that troop.
Just an idea