LEAGUE SYSTEM

I am just confused as how this normal/aram and dominion league system works on?...I just got upto gold in kills few days back and was thinking how more kills do i need to reach platinum diamonds and above...Just a quick notice i m not talking about Ranked...just normal games league system based on KILLS/WINS/CREEEP SCORE..Any help would be appreciated..as this might be confusing for many...And league would help me set a goal!!