First water change..?

Hello new reefer here.
Just getting my tank cycling and got a few questions for the mean time. Im using bio spira and table shrimp for cycling my tank and it just got past the ammonia peak so most of the cycle is in the nitrite and starting to get a little reading on the nitrate. So when should i start doing water changes? Im not sure if i should wait for most of the cycle to complete or if i should be changing the water throughout the cycle. Also Im planning on adding gfo in a tumbler and not sure how ill add carbon but im thinking in a media sock(if anyone has a better idea let me know but i am limited in space so i think this will be my best bet). Anyways when should i start adding the gfo and carbon to the tank? or does it not matter and i could start running them right now.