I'm going to be 100% honest, I can't speak from personal experince because mine have always been an outstanding body part. I have helped some guys bring theirs up though, and I have seen some guys that have made progress. Everyone is of course, going to be different. Some guys are going to need higher reps than others, but one thing is consistent. You want to squeeze and get a full stretch. Don't bounce on the movement. Standing calve raise machines are what I think works best. I would do 4-5 sets, 3 times a wk. I would squeeze for 2 full seconds at the top and stretch to full extention. Use a weight that you can get 8-12 hard reps

In the end, I believe that calves are highly genetic. Still, even a guy with poor lower leg genetics can improve