The Cat Merchant will offer deals from time to time. They usually are not in your favor. Do not accept any of his deals until a few days or until you know your cards perfectly and that you will be better off accepting his offers.
CPU battles
When facing the CPU, take advantage of its defensive weaknesses. Balance between attacking the hero and the cards it summons. Place high defense cards in front of its heroes.
Decks
With the correct cards, having a single or double-element deck can be very powerful. If this is not possible yet, mix and match three elements and try to keep their numbers equal. Also consider getting two very powerful cards from an element then mix the other two slots with lower value cards. Keep a balance between support and action cards and actual front line cards. Try to make your deck as flexible as possible.
Leveling
Level up as soon as possible to increase your cards' stats, gain resources and get the ability to play more actions per turn.
Resources
Resources are rewarded randomly. If possible, play all available cards before using new resources. Watch for cards that may give or take resources from you or your opponent.
Reviving
After you are out of cards that can be played, revive cards that were destroyed by spending some of your Health Points. Only do this after you have lost at least four cards to make it worthwhile.
Cat Merchant...