My notes of Episode 1 summary:
Chang Ge's mother warns Li Shimin about Crown Prince's plans (We later on find out that this allows him to plan out his next step and put up his guard against Crown Prince)
The Cuju Game (A'Sun joins in the game to test out and learn more about Tang's forces)
It's also the first episode, so some of the key players/characters of the drama are introduced, and we get to see a bit of their personality and essence.
It is also the first meeting between Chang Ge and A'Sun.

Based on these observations, my idea for the name of episode one is "Know Your/Thy Enemy"

Another name I have is "Prelude"

WK1 says that episode 1 is like an introduction, the set up for all of our characters and plotline.
Biri_biri pointed out that first episode is the starting point of a great change for all characters.
HappyBirdEgg states that episode 1 is the calm before the storm, events that occur before everything went downhill for Chang Ge.
Grizzy Ashe makes an interesting connection to Shakespeare's play that has a similar hidden meaning---the battle has begun.
And finally Royals mentioned the reversal of luck and unexpected encounters that the characters face.

Hence I think "Prelude" might be a good title, for it means, "an action or event serving as an introduction to something more important." Another definition for "Prelude" is that it's "an introductory to a piece of music." The name of the drama is The Long Ballad. So the prelude could also mean introductory to the song, the introduction and starting point of Chang Ge's ballad.

Additional or increment notes to Songfalcon:

In episode one A'Sun already met Changge twice. Once at the street in Chang'an. He knows from the first meeting, CG is a high level court official of some sort.

2nd meeting was at the Cuju game. He was very impressed by CG's military knowledge and athleticism.

That little dagger that Changge won, that would be important instrument for Changge. She would later used it to try to kill Li Si Min, and later, as a bargaining chip with AS. And later as a symbol of restoration of relationship with Li Si Min.

We also learned from E1, Changge learned horse riding, martial art and military strategies from Li Si Min. CG gifted that sword to Li Si Min, as a token of appreciation for what Li Si Min taught her.

My label for the 1st episode: Introduction