Back to school? SEO? Graphic Design? Computer Science? The burning questions...

I handle all the marketing and advertising for multiple businesses in my town. I am intrigued by this business and love trying new things. I have lots of ideas on how create landing pages, pack them full of SEO and create campaigns around them. My problem is that I don't know how to build the sites. I know how they should look and where to put calls to actions. I also know how to advertise them. I just don't know how to build them. Should I go back to school for something like this? Should I go graphic design? SEO? Coding? I want to make myself the ultimate package. Any ideas?