I'm not 100% sure but I think creeps don't give you gold at all, so you would be limited to the set amount of gold you get from your citadel. I don't think it would be a good option to not get any gold for kills, but the amout of gold for kills should be reduced, by 50%.
Creeps do give you gold. More gold for the more powerful creeps.
As for the gold from demigod kills, this is why I mentioned it would be a good option to choose during custom games, this way you can make sure everybody can agree (or even title the room name as such) so they all know what they are going into. I wouldn't do it very often as I think the gold system is fine, but this was generally a suggestion to help that part of the community that is having a problem with it.