Multiplayer fighting system

Hello guys Nice to meet you! This is my first time here on forum, and I'm think to create a multiplayer game where we will want missions and pvp. This game would have a fight mode like Grand chase as well just a o team would win... Can Somebody would give me a suggestion about how to do it and some tips? I was think a fight like the "Grand chase" had, but how I would get the win team, better char, final rank?

Grateful now and thanks for your patience!