I'm pretty familiar with the broad strokes of Western society from the Greeks to the middle ages, by what was it like in the Pacific? What was their monarchy/ tribal chief/ leadership like? Were they mostly farmers or did they mostly hunt and gather? What was their religion like? How small was too small when finding a new island?
Just give me a general sense of normal life in the area.
The Pacific encompasses over 1000 different cultures and languages, so it's honestly pretty hard to give a straight answer to a lot of these questions since it will vary a lot. Ignoring the Papuan cultures and focusing on Austronesians, they are primarily farmers and fisherman. They often do a lot of spear-fishing which I guess you might consider a type of hunting. On some islands hunting game on land might be more or less common. On low-lying atolls for example, there's no need to 'hunt' since the island is so small. Generally, men will hunt and fish. In some cultures men tend the gardens, in others women do. Staple crops vary a lot from region to region. Coconuts are a staple pretty much everywhere, but the main source of starch and carbs differs. In Mirconesia, breadfruit is king. In other parts yams, banana, cassava, taro, sago, sweet potato or a mixture of the above are common. Most of the pacific has pigs and chickens, though pigs weren't brought to Micronesia.
Political structure and gender roles vary a lot too. Polynesia in general was very patriarchal, whereas in Micronesia women tend to hold a lot of political power. Most of Micronesia is matrilocal, meaning men move in with the wife's family. It is also matrilineal, meaning that inheritance (for both men and women) is derived from the mother. In the Marshall Islands, there are two separate lines of chiefs for each gender. The male chiefs are called irooj and the female chiefs are called lerooj (historically from combining le- 'woman' to irooj). If an irooj and a lerooj have a child, the child is an iroojlaplap or leroojlaplap, a supreme chief (literally chief-big-big). Each irooj and lerooj are responsible for and own 1/3 of an atoll (sometimes a large atoll might be split in half with two chiefs owning one half of the atoll). Below each irooj are several Alaps who own and have control over an islet or part of an islet. Below each Alap are the ri-jerbal each of whom own a weto or tract of land. Each ri-jerbal is entitled to 1/3 of the production from that land. Their Alap is entitled to 1/3 from all the wetos they precide over and the irooj is entitled to the bounty from the atoll they control. Large parts of this traditional political structure were written into the constitution when the Marshall Islands became independent in 1987 and are still practised today. I have witnessed an iroojlaplap land on the island I was staying on in his private yacht, shake everyones hand, collect about 100kg of food and take off that evening.
How small was too small when finding a new island?
Obviously an island needs to be big enough to support a small population, but generally more limiting factors are whether there is a sheltered bay or lagoon, soil quality, and climate.