To refill your energy meter you'll need to have to either wait for the timer to expire or level up. You'll receive an energy point back every minute or so, but if you want to get straight back into the action, you'll need to buy an energy potion from the in-app purchase store.
To change the cards that feature in your adventuring party by tapping on the cards icon at the bottom right-hand corner of the main screen. Here you can swap out one of your current creatures for a new one.
If you don't want to watch a battle play out in its entirety, hit the fast-forward button in the middle of the screen. This will give you the result of your automated combat immediately.
Don't let unwanted cards go to waste. You can use them to enhance one of your favorite cards by tapping on My Cards, then selecting Enhance. Select the card you want to improve, followed by the one you want to sacrifice.
To take part in the Player vs Player (PVP) system tap on the Battle icon to view a list of available opponents. Be careful who you take on though - the crossed swords icon value next to their portrait should be less than your own unless you want to take a nasty beating.
It's worth taking part in as many PVP matches as you can each day, as the leaderboards are reset every night. The higher your performance on the leaderboards, the better your rewards will be for participating.
As you level up you'll receive skill points that you can invest in your character. If you find yourself running low on energy a lot, invest points into your energy level. More battle points will make you stronger in PVP, while investing in your library allows you to carry more cards. Dying on the battlefield? Throw some points into your health levels.
If you want to get your hands on a Legend card set, hit the Refer-A-Friend option. You'll need to share details of the game with a friend via Facebook or e-mail. Once they've signed up, you'll be able to claim your reward.
Keep an eye on your Goals, found in the tab at the upper-left of the screen. Completing these will give you coin, card and potion rewards which will keep you player for longer.