If he is going to promote it here in the forum I think it is just a waste of resources to hire a marketing manager where he can ask a reputable manager to handle the promotion he can do here in the forum or are you referring to the manager here are the marketing manager? If you are referring to the managers here I think that's a good idea since they are more expert and more experience in marketing here.
Op don't need a marketing manager to advertise here on the forum. The manager can help manage the campaign so he will not have to stress himself or spend much. There are different campaign manager that he can use to advertise here with good reputation. If he intend to adverse a gambling platform, them I know that will be a good idea cause their are many gambling platform here too that are using signature to advertise here.