You really should start with the first one, Origins, if you want the full story. Inquisition has fun gameplay and a beautiful open world to explore, but the story and events may not make sense if you haven't played the previous games and there's lots of little bits and pieces that reference previous games. 😊 If you couldn't make it through the first one, then definitely start with Dragon Age 2 at least. The events in Dragon Age 2 is what has led to the events in Dragon Age Inquisition.