I'm pretty sure some of the purchases were about money, Napoleon sold the Louisiana territory to pay for his military and wars in Europe. This was a time when money was gold and silver and any tampering with the purity of it would quickly lead to inflation.
I think it would be much more difficult to be legitimized as just a group of people. Hell, real populations of hundreds of thousands with land and towns and cities aren't even recognized in the world as it stands. Republic of Abkhazia, Republic of South Ossetia, Nagorno-Karabakh Republic, and the Pridnestrovian Moldavian Republic for starters.
It seems like just going and getting some land and living on it is the best first step.
Napolean is a very special case. He was anti-banker. His war was against the banks.
In america, there is lots of land. Lots of it, just sitting there doing nothing. And it is controlled by the BLM (Bureau of Land Management.) They say they own it, but the United States of America cannot own any land. So, legally it is all up for grabs, and all you need to do is stake a claim.
However, do you remember a little thing called Waco Texas? Where a little group was becoming self sufficient , and the govern-cement had to come in and put a stop to it. Where the govern-cement came in and killed everyone, including women and children by cyanide poisoning. And then they buried everything, literally. And this is supposed to be one of the better govern-cements on the planet.
If your plan is to become a country, getting land first is a bad idea.
If your plan is to become a group that doesn't owe fealty to anyone, then start your commune but do not advertise.
Well, I don't suspect anyone will do it. This was all just a kind of what-if thing of possibilities.