The deck consists of 3 parts:
1. The core: You will mainly attack with this part of the deck
2. Defense: 2 spells to defend against enemy attacks
3. Throwaway cards: These cards should cost low elixir, and aren't part of the strategy.
List of cards:
Skeleton army: Very high damage if you don't counter it, can go well with even the throwaway cards!
Mini PEKKA: Another high damage card, bury it in the skeleton army or make it hide behind the giant for maximum use.
Giant: A shield, can be used to support the above.
Baby dragon: A great area damage troop, can be used to prevent the enemy from swarming the giant or mini PEKKA.
Arrows: the classic counter to a swarm, you should always have more than one.
Fireball: used for eliminating "nightmare" troops like witch, finishing off crown towers, and destroying buildings. Swap to rocket once in arena 3.
Goblins and spear goblins: the "throwaway cards" we talked about. Replace either with skeletons when you unlock it.
How to use: You should have at least 2 of the core assault cards. Otherwise, you should deploy your throwaway card(s) and then deploy 2. Add a throwaway card if you like.
If you have giant, deploy it in front, and then the other card after.
Otherwise, deploy both at the same place. The mini PEKKA/baby dragon should be right in the center of the skeleton army, if you use it. If you use mini PEKKA and baby dragon at the same time, they should be on top of each other.
Use the arrows/fireball if you encounter a serious threat.
The weakness of this is the witch. My advice is that you BURN the witch with a fireball or distract her with a giant. If you cannot, then it is a serious threat to you. You need to let it pass. Hope for the best.
If your enemy places a building on one side, use the other. If it can attack both sides, take it out with a rocket. If it is a cannon/bomb tower, use a baby dragon. Spawners you might just want to wait out.