The game has 12 chapters, composed of QTEs (quick time events) and fixed battles. You cannot select your favorite fighter but the game will make you control the main character of the chapter you're playing. Completing the story mode will unlock new stages and also the locked character, Shinnok. The story mode will bring players a cinematic experience since cutscenes and events will take place right before they get thrown to battle.
The battles should be easy enough for you to manage. If you're still having difficulties defeating your enemies, you can change the difficulty settings in the options menu. If you're still having problems, you can skip the fight. By default, you have three Skip Tokens. You can get more from the Krypt.
Furthermore, you can earn Koins (currency to purchase Unlockables from the Krypt), profile experience, and faction experience.You can even get the chance to fight some of the non-playable characters in the game (like Sindel and Baraka).