So you've chosen a Region and a Religion (if any) and a basic Government, Economy and Society. Whether you knew right away or agonized over the choice your new baby-city has a name and officially exists as an independent state. Now you live in a near-empty granary with all your worldly possessions and the handful of peasants who were sort of living nearby when the Granary went up. There are many paths you and your new settlement can take from here, the options formed by the world you started in.
Will you be able to trade a single export for everything you need on the world market or are you alone in a vast wilderness? Have you settled in a friendly area or are you surrounded by scrappy raid-happy rivals? Are you a Rank 1 scrub hoping to make it big or a powerful ex-Minister/Adventurer ready to make their mark? These circumstances will shape your original choices as a Sovereign. For the sake of this guide, let's assume your'e low rank/lvl and you want to be relatively self-sufficient. This is a surprisingly challenging task and will take some effort to set up.
The first thing you want to take inventory of is your inventory. Your personal inventory represents the entire storage and treasury of your Settlement. It's size is based on your character's current Might score and the storage of all your owned buildings. If you have received a settlement-starter-pack, you may have a few extra items like canvas, wool and bricks. You may need these for housing buildings soon, make sure you don't lose them without a plan. If you over-fill your storage, the extra is not lost. It stays near you as overflow for less than a day before getting lost. You will usually lose units of your 'least valuable' items, but this may not be according to your plan. Don't leave overflow to chance.
The Grain Situation
The first thing you may notice, wondering what to do with your brand-new Fields district, is that both Granary upgrades and Farms cost grain. This means that Grain represents your original expansion options. Build as many farms as your current Grain stores can support (more Grain can be acquired through low-level actions) and set at least two of the farms to produce Grain at 100% employment.
A quick check through the blueprints (found on the third tab over the district map) will reveal how many low-level buildings require Hemp to build. Additionally, the Fishing and Residential districts require Hemp to get started, as do both the exclusive and linked buildings in the Forest Outpost, so set 3 more of your new Farms to Hemp.
You, the Sovereign are too busy to take a day-job in any of your buildings, so even this early Exemplar players are useful. Lord or Hero characters can take jobs in any buildings that offer employment. The first 5 residents can live in your Granary and their occupation will provide you with up to 50% free employment in the building they work for. This means that setting your employing building to 50% employment/production will cost no NPC employees, and setting it at the new 150% option will only cost 100% of NPC employees.
Research positions are special. They do not augment NPC work but instead unlock Research Points in Science and Technologies. I highly advise getting at least one Exemplar-resident into your settlement to take the research position offered in your Granary. You will then want to set your Granary to research the Granary building for your settlement. This will soon allow you to upgrade your Granary and start researching the next upgrade.
Your Next Districts
Until you hit Rank 2, you will only be able to build Rank 1 Districts, and only 3 districts before you build a Town Square and raise your Settlement to Rank 2. This means that you can only build 2 of the 4 options available to you before you must build your Town Square (out of Marble no less).
The Forest Outpost will eventually be necessary for a self-sufficient settlement, as it is the only place Lumber (for Boards Boards) and Pulp (for Paper) can be harvested. It requires animals to build, which you don't currently have a way to harvest with buildings. This means you will either need to buy the animals or Trap Animals many times to build this district. If your local market is flush with cheap Lumber, you may decide to skip the Forest Outpost at this juncture.
The Fishing Outpost is not necessary for anything in particular, but is the lowest-rank way to create and store boat-units. Fishing Piers and Fisheries, the buildings that provide oceanic-sourced items, can be built in any district. If you (for some reason), have access to the resources and technologies to create the boats, this is a pretty good investment (it's only Hemp).
The Residential district is easy to build (Hemp comes in pretty fast) and relatively important. Improving your Granary is a great way to house your population at first, but eventually you'll need to provide family homes for your NPC population. The Residential is a great way to concentrate that population (and Happiness cost) in one district. If you have Marble, you can now choose to use Villas instead of Latifundia to house your Peers.
The Palisade Line district requires either the purchase of lumber or the producing it from your own Forest Outpost. This district does not offer any benefit in terms of the production chain, but if you're worried about your Defense Rating or Security Happiness, the Palisade is one of your earliest solutions.
Quest for Marble
The Mines district is not available until you've built your Town Square, but your Town Square takes Marble. This means you'll either have to buy the marble or build a Quarry in one of your existing districts. Quarries take a lot of NPC workers, so Exemplar workers and/or extra housing at this moment may be required. Remember to set the Quarry to Marble, they try to harvest Sandstone when construction completes.
Sovereigns who want to skip the rogue Quarry step can choose to buy their Marble from the Market. If the player-market supports it, you can try buying the slabs for farm products. Alternately, the game-market has every item in the game available for Platinum if you have some and want to spend it.
If you haven't reached Rank 2 by the time you're ready to build a Town Square, don't fret. Work on managing your first 3 districts and getting the hang of being a sovereign. You may want to investigate all the Linked buildings (can be seen in all district blue-prints) and planning your future production. Build up your stores and population, gain player residents (a great source of Importance) and get to know your neighbors. If they need something, they might help you start producing it. If they're hostile, you'll want to know. Don't forget housing buildings or all your industry buildings won't work.
There may (or may not) be large, dangerous settlements when you found your new city. Fortunately, unless they're rolling in Platinum and have managed to create several hundred down-votes against you in the forums, these military powers are unlikely to harm you. The game ensures that attacking (and allying with) settlements of un-equal rank is both difficult and expensive. Your biggest risk will always be Settlements close to your rank who have focused more on military powers than you have.