Or just start with the history of the US Martial Handgun from early revolver to today and then build on the theme later.
Colt 1860 Army (Uberti copy).
Colt 1872 Peacemaker (Uberti Copy).
Colt or S&W .45 ACP revolver, Model of 1917
Colt or Smith & Wesson .38 service revolver (pick the opposite manufacturer as from the 1917 above).
Beretta 92 nee M-9
That's a nice representation of from a number of different viewpoints: Martial, revolver v/s auto, and the general history of the repeating handgun from cap and ball to today.
After that you can branch out into filling-in different Colt and S&W revolvers, and see what else you end up being interested in. Think about adding samples from the adversaries: Walther P-38, Luger, Nambu, etc. Think about adding arms of the Allies: Webly, etc. Then perhaps rifles, then... well then let your mind and budget dictate. It's a lifetime of education to enjoy. The study of the arms leads to a study of history, and that's the beginning of an entire holistic education.