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 ;-)