All of it is what I suggest, music paper, books and recordings.
2, Find the public or private Classical radio station in your area and tune in to it 24/7 or as much as you can, home, car, work, etc. Get it in your head..
3, JOIN a local Community Orchestra, today or tomorrow. Do not wait.
4, Get a pro Classical bass teacher to help make it all work.
Now, you will be finally approaching all the DB was made to do. Jazz is great, I love it but after avoiding Orchestra work for about 35 years I finally realized what I was missing. Now I get a bit of work here and there playing it in a few orchestras. I don't know how I said 'no' to this in my mind back in my younger years but I did and if I could be 20 again, I would be working to get into an Orchestra and doing it thru College as well.
Do all you can do from what I posted. You will thank me later, over and over again.. Hopefully..