I have had a number of people email me saying that they are interested in starting a gun collection, and what would I say they should collect? I think this is a fundamentally erroneous approach to the question. There used to be a sort of understanding that “Gun Collecting” meant a specific group of community-approved “collectible” guns, most notably Winchester lever actions, Colt and S&W revolvers, Mausers, and Luger pistols. I disagree with these artificial limitation in the strongest way. I think that the whole point of collecting firearms is to find a specific theme that you personally find interesting, and build a collection to gain a better understanding of it. That can mean shooting a thousand rounds a week or never firing the guns at all. It can mean collecting based on a country, a manufacturer, a time period, a mechanical action type, a specific conflict, a specific country in a specific conflict, a caliber, or really any other factor one can imagine. I have a friend who collects sporterized pre-1898 military rifles. I have another who collects guns all with the same serial number. The essential element is that a collection is based on your own personal interest. It is irrelevant whether your interest is shared by a million other collectors or by nobody at all.
If you want to begin collecting firearms, you need only consider what piques your curiosity and interest, and follow that thread. My apologies to your wallet in advance!
Also, buy books first. A few hundred dollars of books before you buy a single gun will save you a tremendous amount of money in the long run.