How would I create a Tournament site

Hi, im here to get advice on how i would create a tournament site similar to gamrs.net i want it where players can create an account, make a team, invite their friends to that team, and join the team into a tournament that we would be hosting! It seems very simple but complex at the same time. If you have any ideas or can help me, please respond! If you would like to work with me, my skype: hobosacks9

Thank you, and please help!