Seven Important Things
The intended focus of the campaign is exploration and kingdom-building. There will be quests offered, dungeons and adventure sites to explore or ignore, and NPCs with their own agendas, but ultimately, this is the story of the PCs, of where they go and what they do. No powerful patron or outside influence exists to direct or support the PCs in the creation of their kingdom, so at least one PC should be strongly motivated to do this. On the other hand, there is no outside pressure nor built-in expectation that the PCs should begin building their kingdom at any one point in time; the PCs have as long as they like to accumulate the resources they'll need and to make friends and allies.
The campaign is intended to run bi-weekly for roughly a year, and will use the medium XP track. Past experience with Pathfinder suggests that PCs will level up no more quickly than once every 3 sessions, and thus, the highest level they will attain is 8. With that in mind, and considering Pathfinder's recommendation that encounter CR should be no more than three levels above the average party level, no single creature or keyed encounter in the campaign will have a CR higher than 11 (though intelligent enemies of any CR are not bound to play fair).
The campaign takes place in a homebrew setting, in which the largest local power is Jaoshen, the Phoenix Empire. This is not a historical campaign, but Jaoshen does draw inspiration from real-world nations and historical periods, in much the same was as many nations of the Pathfinder setting (Brevoy from Russia, Minkai from Japan, Ustalav from Transylvania, etc.). In this case, Jaoshen draws much of its inspiration from Joseon-era Korea and Ming Dynasty China, though other influences (the Ayutthaya Kingdom, the Khmer Empire, the Tibetan Empire of Bod) are also present at a local level in different parts of the Empire.
The world is young, by the standards of fantasy game worlds. The Phoenix Empire itself is in its 737th year, with the recorded history of the mortal races dating back a further nine centuries or so. Before this, the world was ruled by giants, and the races that would later come to dominate the world lived as either slave races to the giants, or barbarians, driven into the most inhospitable corners of the world. Anything beyond about 1,600 years ago – the age of giants, and whatever came before – is a mysterious and mythic time, from which only unverifiable stories, cyclopean ruins, and strange artefacts remain.
The Phoenix Empire is powerful, but preoccupied with its own concerns, and the PCs should be free to pursue their own goals and advance their own agendas within the Lost Province without Imperial interference. PCs who wish to dabble in the Empire's politics can create their own opportunities to do so, and overt action against the Empire (such as claiming hexes in the Far Province) will certainly provoke a response, but in general, the Empire will be no more active a player in the campaign than the PCs want it to be. Exactly what transpires when the PCs' kingdom grows large and powerful enough to come to the Empire's notice may, if nothing else, form part of the campaign's epilogue.
Most people in the Empire worship the Twelve, Jaoshen's patron gods, named by the first Phoenix Emperor as especially deserving of worship. Not all of the Twelve are worshipped with equal fervour throughout the Empire, but all of their cults, broadly speaking, respect and support one another. The people of the Empire refer to gods who are not part of the Twelve as 'the Hundred' (their true number is unknown, and probably much higher than one hundred) and generally accept their worship where it does not conflict with the tenets of the Twelve. Animism (the presence of spirits in animals, plants, places, and objects) and the reincarnation of mortal souls into new lives are both facts of life in the Empire, and colour the religious beliefs and practices of its people.
Many different races live in the Empire, of which humanity is simply the most populous. All of the Core Rulebook races are known throughout the Empire and will be treated with some degree of civility; many of the races presented in the Advanced Race Guide are likewise known and accepted, although to what degree varies from race to race. The Phoenix Dynasty is a human family, but the Imperial Regent who ruled the Empire for almost three centuries prior to the Restoration was an elf; his race was never a point of contention. Individual communities may be cosmopolitan, elitist, insular, or have opinions on particular races informed by local experiences.