I believe you is the indirect object. Love and Affection completes the thought. You can be left out. I'll edit this later if I'm wrong.
Answer:
Watch the movie and then buy his sister a gift she will enjoy.
Explanation:
The given passage from "The Quinceanera" shows how the narrator was in a dilemma on what to do- either get his sister a gift or go to the movies which he had already planned to see. He knows he has to get the gift but he also did not want to miss the movie.
And then, he mentioned that his sister loved movies so maybe he can get "two birds with one stone". He will go to the movies and get her move tickets for a gift, which simplifies his dilemma. So, going along the narrative, we can best predict that he will go to the movies and then get her a gift she will enjoy.
Thus, the correct answer is the third option.
