Classical music newbie needs your suggestions

I’m a newbie as well! Slowly, very slowly learning... It’s a vast world, with many periods / styles / composers, then of course you have the many interpretations / directors / orchestras (they can be VERY different) modern instruments vs ancient instruments...

Without going into the various interpretations, here are some works I really like; mostly vocal / choral works but not only. Choral works are also a good test for your system... you may believe your system sounds good until you hear Mozart’s Requiem and it sucks. Beware! ^^

So:

Mozart: Requiem (of course)

Mozart: Exultate, jubilate

Beethoven: piano sonatas

Bach: cantatas (there are many)

Bach: magnificat

Pergolese: Stabat mater

Vivaldi: Stabat mater

Vivaldi: opera arias (I mostly don’t have the patience for a complete opera, yet - I do, if I see it live)

Rossini: Petite Messe solennelle (no idea how you’d translate that in English)

Orff: Carmina Burana (I really like the 1968 Eugen Jochum recording)

Handel: Messiah

Rachmaninov: Piano concertos

Non exhaustive list, of course, and I’m sill learning myself, so... and yes, a lot of religious music, and I'm not religious at all myself but, those pieces are splendid and would - at least- keep your spiritual side, no matter how big a place it takes in your life, alert ;-)

The symphonies of Carl Nielsen.

After more than fifty years of trying to educate myself about classical music and listening to thousands of records and cd's on fairly good stereo systems, I had the time to listen more seriously during the pandemic. I intuitively began to focus on one composer: Mozart. I learned that I loved his chamber music the most, and eventually branched off to others.

I actually found some of Mozart's works difficult to listen to at times because of the sheer emotion that arose in me when I began to appreciate them. This surprised me, incidentally, because there is also a lot of humor to be found in Mozart's works: this is what initially attracted me to Mozart when I "rediscovered" him.

I have a nice beginners collection of Mozart that I return to when I get the urge, but lately my journey led to rediscovering Beethoven's piano sonatas (specifically Alfred Brendel's interpretation), and recently Hayden and Scarlatti. The latter artist took most of the fifty years for me to begin to fully appreciate. 

That said, I found that my classical music journey resulted in what I could only describe as a spiritual one as well when I devoted myself to Mozart. My advice it to forget about all the rest do the same. 

Aaron Copland- I call it frontier music.  Rodeo, Billy the kid suite and Appalachian spring. The music brings to mind any western movie and a nation bursting into west.  

There are lots of good suggestions above which I will try not to repeat. Here are some I highly recommend:

• Bach - Brandenburg Concertos
• Bach - organ music, especially Toccata in F (BWV 540), Prelude & Fugue in A minor (BWV 543), and Prelude & Fugue in D major (BWV 532). Since this is an audio forum, you have to test your woofers with some really low bass, and only the pipe organ can really do that (16 Hz). 😁
• A Bach Festival, Empire Brass and Douglas Major, organ
• Music for Organ, Brass, and Percussion, Empire Brass and Michael Murray, organ (Telarc).
• Handel's Messiah
• Saint-Saens - Symphony No. 3
• Charles-Marie Widor - Symphony 5 for organ
• Rachmaninoff - Rhapsody on a theme of Paganini, all four piano concertos, 24 preludes for piano.
• Holst - the Planets (especially the Charles Dutoit/Montreal Symphony performance).
• Basically anything by Tchaikovsky.
• Sibelius' violin concerto.
• Smetana - Ma Vlast, especially the Moldau.

I'm sure I can think of more if I look at my CD collection, but that's a good start. Have fun!  Some of these will take multiple listens to really understand, but they're all great music.