In duel of fate game, just tap twice the menu button to bring up the footer that shows your open apps in order to get more cards.
Always pick two different types of cards, rather than two of the same kind of card such as fire beats plant, plant beats water and water beats fire.
If your card has a power level of 30 or above, you will be able to defeat more powerful cards.
Just try to most often pick the cards that do extra damage after they are victorious against another card, such as the Fire, Spring or Ice Spirit cards.
Note that your deck of cards is optimized at all times, as you will win a lot of cards in battle including more powerful ones you.
In the inventory screen, the cards will be organized first by type such as fire, ice, or spring then by their power level, from highest to lowest.
Put only the highest of each power level in your deck.
For example, if you have an unused 35 point ice card in your deck, and a used 28 point ice card as the lowest ice card in your deck, you want to take that 28 pointer out of your deck, and you can add in the 35 point ice card in its place.
Just try to load up on either health potions or claymores on the main menu.
Use your claymores with your weakest cards when they come up, but if you have enough claymores to do so, use them as often as possible in order to beat opponents much more quickly.
Try to get two claymores in one turn, you can use both of them on a weak card or hell, on any card in order to have a victory quickly.