What do you mean by a functional website?
Websites nowadays are mostly: complex applications (think gmail, google docs, google maps, spotify for web), front ends to large server applications (bitcoin exchange, search engine, etc) or simple web pages (blog, company websites).
- If you are just talking about a couple of webpages with information you don't need to do any programming really.
- Are you talking about creating a platform for trading (graphs, etc), in that case you probably want to look at client side stuff like javascript (and some server stuff to keep xxxx websockets open).
- If you want to create something user oriented like a community or something you probably want to invest in server side stuff like python (maybe the django framework), ruby (RoR) or even PHP