you cannot get the GS ball in crystal english version... so of course nobody can really help you with that.
GS Ball exist in the japanese version. You can get the GS Ball from the Goldenrod Pokemon Center (that is twice as nice as the english version one) after getting all 16 badges. Then using the mobile adapter, you gotta win the Chieko and Dice game 3 times in a row. Also, you have to answer the card quiz 10 times correctly. Upon leaving the Goldenrod Pokeon center again when you have done all of these things, you'll get the GS Ball.
Take the GS Ball to Kurt, and then the next day go to see Kurt again. Get the GS Ball back and enter the Ilex Forest, towards the shrine. Battle lvl 30 Celebi there.