Are you looking to build you best cards to win against your opponent? I will help you with that problem, after my hard search all over internet, Google and Youtube, watching tournaments and youtube clash royale battles, I have found a top 5 cards that might be helpful for you, these cards can obtain on a low level and low arena but these cards can surely help you along the way to top 5+ arenas, look at the breakdown below.
Giant can obtain at start of your account, when your on training , you already have this card. This card has a high HP so this can tank the tower damages.
You can deploy the Witch for only 5 elixir and the Witch have a 3 minion that has decent amount of HP that can fairly tank the enemy and also has a damage to kill enemy. This can also obtain while on training camp.
The Prince is a high damage card, it can destroy one tower by himself (yes you heard it right), this card can obtain at the training camp and only require 5 elixir to deploy.
This guy and his ride targets building and he can also jump over the river, Hog Rider only require 4 elixir to be able to release and destroy the enemy’s tower. This card can obtain at the P.E.K.K.A Playhouse arena 4.
Balloon can be unlocked at the Arena 2 Bone Pit, this bone also love to destroy buildings like Hog Rider but this has more damage and can destroy the building in just 3-4 attacks. You need 5 elixir to make him fly.