You can win in 3 different ways:
1) Monopoly Victory - This means having a base on each tile in a region. Some regions are 3, while others can be as large as 5! This is an instant victory.
2) Bankrupting Opponents - Bringing your opponents to less than 0 Gold through Battle, Skill Cards, or Tolls.
3) Most Gold Victory - Having the most Gold at the end of the 12 Turns will also give you the win.