You are at the beginning of the game and have not all cards, so you have to earn by opening boxes. We list here therefore gradually both simple decks that you can use relatively early, as well as more specialized decks, which you can use only at a higher level to take the battle.
Battle Deck (Arena 6)
Wait with this deck initially until the elixirs bar is full and the enemy attack you first. Counter him using his own building and units as barbarians, the baby dragons or arrows. Attacks then with a counter-attack and supports the above units with the prince, the magician or the P.E.K.K.A. After a successful defense phase you can beat back particularly strong.
Starter Deck - Low Elixir (Arena 2)
With this deck you can always send troops into the arena, as the elixir cost of all units is small. Set the Skeleton and run with the Knights and Goblins ahead. Behind attacking archers, spear leprechauns and the bomber.