I think a very organic soil would be wonderful. composted etc. Gingers can tolerate some bad soil but if you want them to be lush and bloom well then the better the soil the better and healthier the plant which should lead to bigger fuller blooms.organic fertilizers such as bone meal,blood meal etc are great. I often use soil from my chicken pen, very high nitrogen so must be used carefully, I burnt up a bunch of cosmos this year by using to much at one time. They got five feet tall and bloomed pitifully then died.
James Maloy