I think historical figures are the best to collect. They are usually rare and harder to find and hold their value. The least valuable, over the long term, are sports collectibles. Those autographs are neither scarce, upper deck sports autos are produced in the millions, nor do they hold much long term value especially the cards and autos produced after 1990. There are always exceptions but as a long term investment recently signed sports memorabilia is a poor choice for long term value. Signed books, especially first editions, is an area of collectibles that is still affordable and fairly easy to find. There is still the entertainment industry, including politics, but most of the autographs of today's stars are auto penned or signed by a secretary. Very difficult to authenticate. I would start with books....they are the easiest to find by looking at your local used bookstore or second hand shops. Whatever you collect do it for fun and enjoyment first ...the value will come later.