Mozart Piano Concertos are great for an introduction to classical music. The complete set on London/Decca played by Vladimir Ashkenazy is excellent. If you don't want to buy the whole set, I recommend finding a disc with Concerto's #20, #21, #23, and/or #25, which are arguably the best of the best. Recordings featuring soloists such as: Alfred Brendel, Daniel Barenboim, Rudolf Serkin, Mitsuko Uchida, and Murray Perahia - will almost certainly be an excellent purchase.
Cheers.
Cheers.