looking for ideas on must have classical music

So many suggestions and so little time!

1.  +1 for the above recommendation for Bach's The Goldberg Variations, although I prefer Perahia's performance to Gould's.  Excuse the pun, but for a nice variation on the keyboard performances, try Sitkovetsky's version for string trio.

2.   Shostakovich's 24 Etudes and Fugues for Piano.  I like Scherbakov's playing for Naxos.

3.  Bach's The Well Tempered Clavier.   (As you can tell, I like classical solo piano.). I have Jennifer Hewitt's version, although there are many good ones.

4.  Handel's concerto grosso of Alexander's Feast.  The concerto, not the oratorio.  Just delightful!

5.  Mozart's Piano Concertos, from #18 on up, esp. nos. 21-26, and even more especially the 2nd movement from no. 21 (aka the "Elvira Madigan" movement).

6.  Beethoven's 9th Symphony, esp. The Ode to Joy in the fourth movement.  Well, of course.

7.  Bach's Sonatas and Partitas for Solo Violin, esp. Partita #2, Fifth Part -- the "Ciaccona" (Chaconne").  Menuhin considered it to be the greatest work for violin.  Many, many good versions; I like Milstein.

Have fun!

Forgot one.  Switched-On Bach by Wendy Carlos.  A classic album demonstrating the ability of the Moog synthesizer as a keyboard instrument.  

Wagner Overtures conducted by Sir George Solti. Holst The Planets conducted by just about anyone (I favour Sir Adrian Boult). Vivaldi Le Quattro Stagioni (The Four Seasons) conducted by Trevor Pinnock. Beethoven Symphonies conducted by anyone of your choice. For modern Symphony Orchestra style Leonard Bernstein or Gunter Wand, for "period" style by John Eliot Gardner. Great performances in poor sound by Arturo Toscanini. J.S. Bach Brandenburg Concertos conducted by (again) Trevor Pinnock.

Great performances in poor sound. Isn't that Springsteen?

@blindjim ,
I would concentrate on listening to the composers you have already listened to and listen to more of their works.
Thinking back to my classical introduction, it was on WQXR and WNCN,but they are now either gone or shadows of their former selves.
Unfortunately, streaming services are geared for popular music and tend to have terrible playlists for classical.

Tablejockey has it right-go with the basics.
I would start with Bach, Beethoven, Brahms, and Mozart. They encompass a wide time frame and you can see which style floats your boat.
Bob