The narrator's expectations of what he hopes to find at Araby are very much wedded with the quest he feels he has been given by Mangan's sister, who basically persuades the young boy to go to the bazaar in her stead and get her something. From the moment he has this conversation with Mangan's sister, which is actually the only time they exchange any words at all, he can think of little else. Note how his thoughts become obsessed with the bazaar:
At night in my bedroom and by day in the classroom her image came between me and the page I strove to read. The syllables of the word Araby were called to me through the silence in which my soul luxuriated and cast an Eastern enchantment over me.
The juxtaposition of his fevered thoughts of Mangan's sister and the magic that the word "Araby" exerts on him shows that his expectations of the bazaar are very high indeed, as he views the bazaar with the same kind of romantic illusion that he views his "relationship" with Mangan's sister, who is a character whose real name is never mentioned and with whom the narrator only ever exchanges a half-dozen words. In particular, note the way that the word "Araby" is shown to "cast an Eastern enchantment over the narrator." This results in the boy associating the bazaar with a place of magic, as a kind of Aladdin's cave where he can find objects worthy of Mangan's sister's approval. The reality, of course, is very different, and corresponds with the boy's realisation of the truth of his "relationship" with Mangan's sister.