I can definitely recommend stuff to you. I suggest starting with a compilation, that way you get the best music from every musical period. I believe a lot of stuff that is for sale on Amazon is also available in a store, if you don't like/can't do shopping online. But check this out anyways:
Amazon.com: Classical Compilations.
From those selections, I would suggest compilations similar to this:
Amazon.com: 25 Classical Favorites: Wolfgang Amadeus Mozart, Pyotr Il'yich Tchaikovsky, Antonio Vivaldi, Johannes Brahms, Frederic Chopin, Johann II [Junior] Strauss, Johann Sebastian Bach, Georges Bizet, George Frederick Handel, Maurice Ravel, S. There are some other ones in this series that feature different music so I recommend checking those out too. They all have a similar cover so they're not hard to find.
If you prefer to shop on iTunes with a gift card, I HIGHLY recommend this:
Classical Music News: 24 Hours of Classical Music From Naxos on iTunes. I purchased this compilation about a year ago and I love it. It's only about $10 as well, and you're getting over 300 pieces of music, including Handel's
Messiah in it's entirety. What I like about it is that the music is drawn from every important musical period in history, from Medieval until the 20th century. If you like to burn CD's, it's pretty easy to split this one into playlists that will fit on the disc.
Out of the two that I've suggested, I strongly recommend the one from iTunes. It's such a great deal!
Edit: The iTunes compilation gets all the music from the Naxos Music Library, and I invite you to check out their website as well:
Classical Music - Streaming Classical Music. They have some pretty good articles under the "Education" section in the sidebar on the right
