Different cards will have different uses, and as you get further into the game, you'll see a number of different types of cards, but you'll have to use them properly in order to get the biggest benefit. Your most general-use cards are troops, which will simply allow you to play the numbers game; your goal here is to have more troops than your enemy does, so that you can knock out their troops and protect your castle.

Forts and buildings are specialized cards that should not be used right in the beginning; instead, they should be used as you push the front lines further on. Set them toward the back of your board, so that they can absorb hits from enemy troops and enemy attacks. They'll buy you more time so that you can focus on specific lanes, allowing you to win the castle more quickly.

Spell cards have all manner of attacks, from doing heavy damage to one square to doing light damage to all enemy-occupied squares. For the blanket-damage cards, save these until you get 3-4 or more enemy troop cards on the board. For the single-square spells, save them until a powerful troop is unleashed on the enemy's side of the board - such as the war veterans, which are 7-deep to begin with.

As you use your coins and your rubies to buy more cards, and as you earn more cards from battles and campaigns, you'll come across duplicates eventually. Duplicates are good, as they will allow you to upgrade a card that you already have in order to make it more powerful and effective. Change the filter quality to neutral to see all of your starter cards so that you can upgrade them as needed.

Battle as often as possible as long as you are winning. Each battle period lasts about 14 days, and increase your rank to increase your prize. The lower the rank number, the better the prize. Rank 1, for example, earns you 20 fusion stones. Rank 6 earns you 10 rubies, and rank 14 earns you 80 coins.