When it comes to sociology, there are so many things that you can study. Pretty much the sky is the limit. So, I would say you should study something that interests you.
So, if video games interest you, then you can study the social effects of games. What does gaming do to a person's social skills? Do violent games correspond to violent behaviors and bullying in school? Do games provide an escape for people and if so does it lead to depression or is it an escape from depression? These are all very interesting topics.
As you can see, if you start with something that interests you, you can ask questions that surround sociology.