Which language&OS to pick in this context?

I'not a skilled developer,but i know to program,or simply scripting.At the moment i started a team to create a startup for creating a game. The game will be an MMO(and all the stuff related to this kind of games)running in the browser with 3D graphics,so the main language will be JS+Libraries. The problem comes out about which language to pick to do the server-side and which OS will keep on feet the entire platform. What are your suggestions?