You'd need a solid grasp of a database engine / language of your choice (most likely some derivative of SQL) a solid grasp of a server side language of your choice (PHP, RubyonRails, Java Servlets) and a solid grasp of HTML / JS
since this is what your server side language will output.
Brush up on those, and then experiment away!
Note though that this isn't a small project, and unless you're just doing it for academic reasons there's not a huge amount of point - networks like this exist already. Ask yourself what you stand to gain from the project, or what others gain from it - and if you struggle to answer that question in a concrete fashion, think long and hard about whether it's worth it.