You have to have a good understanding on internt technology specially HTTP. Then study a web development language (php, j2ee, asp). You can make use of thirdparty libraries as you develop but It's not recomended to security intensive operations. My advice is to get some experience first on a dinamic web development and then you will feel when you are ready. And machan never user CMS. I repeat NEVER USE CMS for a aplication like this....
Good luck.