At the end of the Season (every fourth week) you get a reward based on your performance in the Season.

You can find more information about how the Season works and the Season Rank List HERE. 

Your reward is always determined by the Season Points you earned:

Reward = Season Points * 10

So, the amount of Gold you can get depends on your total Season Point in the fourth week.

If you get into the top 1000 on the Local or on the Global Rank List you'll get GEMs too.