I always clone about a week before I change my lights to flowering so the plant can recooperate before the change. I have heard that the gel hormones are better because you have less chance of getting air in the stem, but I have used powder for years with a 95% success rate. I will try the gel when I run out of powder. As pcman said, they are not even necessary so I would just get whatever is available to you. In my opinion, the humidity dome is the most important part of cloning success. good luck!