May one give a present to a gentile?
It is forbidden to give a free present to a gentile that one is not acquainted with. This applies even if the gentile is not an idolater, such as a Muslim. If however one is acquainted with the gentile, he may give him a free present, as certainly the gentile will repay him for the favor.
 151/11; Avoda Zara 20
 Michaber ibid
 Shach 151/18
Ger Toshev: It however does not apply to a Ger Toshev [Shach ibid], which are those gentiles that have accepted the seven Nohadite laws. [Chinuch 426]
 Taz 151/8
The reason: Being that the Gentile will repay him, it is thus not considered like a present at all, but rather like a sale. [ibid]