I havent' heard of using ginger. Do you use powdered or fresh and in what quantities? And same for the garlic? One of the things on my list to find out about / do but for the moment too bogged down on getting my flock all hatched to do anything else!
fresh is always best but I do sometimes use powdered because its convenient and cheap (it does degrade quickly so theres no use in buying alot at once)
with garlic, you can just mash loads up and offer it freely to them, they'll decide how much they need.
sprinkle a treat over the top and make a pecking motion with your hand so they get the idea its food. they'll give it a try and probably love it.
with ginger, i put a tablespoon full of powdered ginger in their water container every now and again.
I also give them free choice of mashed ginger root.
paprika is also great in water. they really love it.
i don't think quantities matter much. it doesn't have to be complicated.