the most experience you can get is out of a real project.
First we start with programming against Oracle with C and OCI.
After that we use PL/SQL for quick alogorithm an less network transfers.
And the last thing we did was tuning SQL statements tuning the database and monitoring running processes and all the DBA stuff
The first step is always the hardest - just do it !
If you have the ability to work or speak directly to a Oracle DBA look him over his shoulders. Ask him.
By the way ... we work with Oracle over 10 years in projects for our customers and in house - but until now - we didn´t understand everything cause there is too much to understand.