I used to love Vivaldi Concerto for Two Mandolins, because of its stereo effect, with one mandolin answering the other. (Some jokers say Vivaldi didn't write 500 Concertos; he wrote one Concerto 500 times!)
If you don't already have it, Carmina Burana by Carl Orff is a 'must' (and you WILL already know some of it from various adverts.)
Easy and enjoyable, is Gustav Holst The Planets, but maybe TOO well known?
A performer I love, who is often on TV is Nicola Benedetti, though some of her collections can be a bit corny.
Michel Camilo is an exciting modern composer and pianist. Here is a brief taste from his Piano Concerto:
All Sibelius Symphonies are amongst my favourites, and you should also have the Beethoven Symphonies. Things that seem 'difficult' at first get easier as you become more familiar with them. If you are not a musician yourself, a good way to listen to Classical music is to try and 'guess' what is coming next, or listen for passages repeating, with slight variations. Count the bars, and hear how things often go in factors of 8; 32, 64, etc. (A bit like computers really!)
The "Bach 48" are quite a challenge. Mozart chamber works are well worth a try.
And if you are really 'broad minded', I love this: