You have gained control of a sizable territory – similar in area to Senegal (~75K square miles). It has savanna and forest, some sea coast with a bay that could use for a harbor, fresh water assets, and an arc of mountains inland that makes the territory easily defensible.
Now, you realize that keeping this land just for you is silly. Well, not possible per se because there are about 3000 natives already living there, their fierceness attested to by the fact that there are 3000 natives living there.
But you have figured out how to reach the natives and avoid being killed by them. Now you want to invite people to immigrate there, because you have a plan for integrating with the natives (basically gradually assimilating them).
So now you have a couple hundred thousand people, who have sorted out a fairly familiar society. It is somewhat stable, but there are flare-ups between people, as one might expect. You decide you want to organize the territory into a nation.
Where do you start? Again, this is you, from your perspective. This nation will probably be named after you. Construct it.
Nations aren’t organised; they develop over generations as a community of people usually connected by birth or descent to a particular place develop shared language, culture, history etc which both connect them to one another and distinguish them from their neighbours. I think what you’re trying to organise is a state.
But to some extent you already have organised a state, at least partly. You control this territory, and you have been able not only to invite a couple of hundred thousand people to immigrate, but to arrange for this to happen. So evidently you have a high degree of control over at least one aspect of public affairs - namely, immigration. Your post doesn’t suggest that you needed to negotiate this with any superior governmental entity. So in what sense do you not already have the bones of a state?
Still, what really characterises a state is recognition as a state by other states. And, nowadays, new states are generally seen to come into existence by the collective exercise by a people of the right of self-determination. So what you need to do is to organise some political structures in the country which will command the support, or at least the assent, of the community, and for those structures to seek recognition as a sovereign state by other states, particularly neighbouring states. They won’t be able to do this with any credibility unless they can show that they are providing effective government to the territory in question, and its inhabitants.
Conspicuously missing from your OP is any mention of the state that currently governs, or claims to govern, or aspires to govern, this territory. There is no inhabited territory anywhere in the world which isn’t claimed by some state, and in order to get recognition of your new state you’re going to have to address in some way the claims of that old state.
The OP is too late. I would have started with and from the people who were already there. They have to be onboard any immigration policies, we need to define them together. And we also need to define together what to do about land rights, schooling, healthcare… they’re bound to already have some structures in place: I would want to absorb those, not fight them.
Which if you think about it is kind of what the multiple governments which existed in Hispania between the 5th and 10th centuries behaved, some with more savvy and some with more big stick. Those who used the stick most heavily used it more between themselves than with the locals, who after all were many more and didn’t really give much of a shit who the tax collector collected for, so long as neither the taxes nor the guards were too heavy-handed.
Governments generally frown upon attempts to seceed (which is what you, OP, are proposing). Even though you may ‘own’ the land, you are not free to do whatever you like with it. The government retains some rights to the land for example, under eminent domain is the right to forcibly acquire your land, or perhaps they retain some mineral rights etc. They want to keep ‘your’ land within the nation state, and will very often fight to do so. An exception is in cases where war has caused destabilisation and the country multi-laterally re-draws borders as was the case in the former Yugoslavia.
The OP doesn’t say that he owns the land; just that he has gained control of it. Actual ownership, in the sense of a registered title, he may or may not have but, as you point out, that’s completely irrelevant to the issue of statehood. Having title to land doesn’t give you any right at all to establish a sovereign state on the land; conversely, not having title to the land is not a bar to establishing a sovereign state on the land.
First, throw all the tea into the bay. Then, get a really big gun and fire a shot that can be heard 'round the world. Next, get a bunch of old guys to sign a document which consists of flowery, vague language that will be the basis of passionate arguments for centuries to come. Finally, establish a capitol so that the lobbyists will know where to find you. Start collecting bribes contributions. Your new nation is now formed and working properly - unless you want a dictatorship, in which case there are the additional steps of shooting half the population and imprisoning the other half.
What does the area produce now? What is the infrastructure like? How educated is the populace, and what is their history? Is there a functioning police force, banking system, and legal system?
First thing is to sign some trade treaties with the more stable countries. Once there is money to be made, they will be on my side, and maybe we can get somewhere.
Regards,
His Imperial and Serene Highness Shodan the First, Monarch of the Executive Washroom and Ordained by God to Be Keeper of the Secret Handshake. Available for weddings, birthdays, and bar mitzvahs. No checks.
I organize a well trained military,
make trade agreements to better my current economic position, and supply my military,
Make defence agreements
Write a constitution, vote on it, and declare that -we- are a nation.
See what happens.