On this web site, you can download lots and lots of old classics to your PC or Mac and then mount the Kindle as a disk. Put the books into the Documents folder. Where to find books here? Look at the top of this page .... about an inch down is a blue bar. Click EBooks, and then choose format Mobipocket for your Kindle.
Then read
this thread about how to buy books from Amazon if you don't live in the USA. Hope this helps!