You can unlock more than 80 total cards that can be used to build a deck of eight. That results in millions of possible battle deck variations, which means there is no single best deck in Clash Royale. Your deck should be balanced between attack cards and defense cards and include single-damage attacks and splash-damage attacks.
The first step in building your deck is to determine the card or cards that will be the focus of your offense. These cards have a single task: destroy enemy towers.
Next, choose cards to defend your towers from enemy attacks. Your choices must include repelling both ground and air attackers. Third, fill out your deck with cards that act as support for the selections you made in the first steps.
One thing to watch while building your deck is each card’s elixir cost. Loading up on expensive cards is a surefire way to leave your towers vulnerable while waiting for elixir to recharge.