I just finished reading all of the Sharpe books, and I loved them. The TV series is great too.
I like to read books in the order the author published them. Cornwell started with Sharpe’s Eagle, then wrote a few more, then went back and wrote Rifles. *Rifles *is a fine place to start, though.
I think the original 11 are the best. I also liked the prequel trilogy set in India, even though he revised Sharpe’s history a bit which I thought was unnecessary and annoying.
So my suggestion would be to read these original 11 first, then go back and fill in with the others.