If you are waiting for your health to refill, take part in Arena battles. Your health there is independent of campaign mode. After three Arena battles, a large portion of your campaign mode health will have been restored.
Attacking
Target a weak point of an opponent will result in a larger hit bonus the first time. However, because each successive hit at that location will have a lower return, begin targeting other parts.
Evolving
When evolving a card, enhance it and its match to the maximum possible level first. Although the product card will have lower stats than the cards used, you can then enhance it again and level it up to higher values than the prior version. Do not waste resources and cards on enhancing low level cards. As soon as you obtain a three star card, begin enhancing and maxing it out.
Extra items
Complete an island and get all the card drops in every area to be awarded a bonus item. Completely wipe out all the monsters in an area to receive card drops, extra experience points, and other bonuses. Log in daily and use the Free Bounty Ticket for a chance to win a rare card. Only go for the three star cards and focus on getting cards in areas that must be improved.
Hero
Fully level your hero first. Try to get one hit kill attacks that will help maintain your health. After your hero has been upgraded, level up your best weapons. After your hero has been set up, start developing your pets. When your weapons trigger a skill attack (for example, Spiral, Bash, etc), trigger it with your Hero. Normally they will do the most damage. However, have your pets trigger the skill attack if they have an element that will results in higher damage.