Is it obligatory for the husband to be courteous to his wife who does not give him gifts, or should he return the gift to the one who does, while observing fairness between the two wives?

A husband must be just between his wives in terms of division (of time), but for gifts and presents, he is not obligated to be just in them, and there is no blame upon him if he gives a gift to one of his wives and not the other, as long as he fulfills each wife's obligatory right to maintenance.