Don't worry about it...pretty much no one gets a build right on their first attempt. There's always ways to tweak and improve. My suggestion would be to spend some time looking at builds done by experienced synthesists on here, as well as studying what makes classic synths such as the ARP 2600, Minimoog, etc the classics they are in terms of module complement, control layout, and the like. Like anything worth doing, doing this takes time and patience.