Firstly, you should look up some guides for terraforming with WorldEdit on YouTube. It really helps, and nobody wants to be playing on maps where the terraforming is just spheres that haven't been smoothed. Have you seen any maps like that on the servers?
Try practicing for a while, and then try making another map, maybe around a radius of 250? Terraform everywhere, not just at the very edges of the map. Use buildings and landmarks where appropiate. Good luck, and I'm hoping to see something good from you in the future