This Graveyard deck is extremely expensive and very beatdown oriented. Focus on defense first and create big unstoppable counter pushes with your graveyard and spells to clear out your opponent's defending units.
The Giant Skeleton is very important in this deck. Use him as a tank for the graveyard but also place the Skeleton king behind him to push him forward to try to get the death bomb to the tower.
The Graveyard is the main win condition of the deck. Make sure one of the big skeletons is distracting the tower when you go for it so the little skellys can build up and swarm the tower.
The Tombstone is very important for defense in this deck and it is also very useful for filling up your skeleton king ability.
In the early stages of the game, play very passively and play defense. Do not overcommit with a graveyard unless you know your opponent will not be able to defend.
In the later stages of the game, it is your time to shine. Play good defense and counter-push with your spells. Play the graveyard while one or both of your big tanks are distracting the tower and use your fireball and arrows to clear out whatever your opponent uses to defend.