Bothe are grammatically correct, but...
The future tense in Korean expresses more of an intention/determination, especially when the subject is "I".
And "receiving gifts" isn't something where your intention/determination matters much.
Therefore, we have to reconstruct the sentences to something similar to: "I will end up receiving many gifts"
A) 저는 크리스마스에 많은 선물을 받게 될거예요.
B) 저는 크리스마스에 선물을 많이 받게 될거예요.
We can say that A) and B) are almost the same, but A) sounds more "mature"
Cádiz? I envy you.