I guess it really depends on what the company defines as a good DBA . In my Previous company i worked mainly as a developer but was then slowly pushed into the role as a part time DBA. I started of by trying to get the basic tasks right , Every DBA role has some amount of routine Tasks that are part and parcel of the job. get them right , the rest are one off issues that your better of learning by trail and error.

I am not a fully qualified DBA but the people in my company feel i am good at it 🙂