1. Humanism, Diplomacy, and Aristocracy are almost certainly your best choices for your first three idea groups. Especially Humanism. With policies and those idea groups, you can get a -60% reduction to accepted culture threshold, on top of the -15% from Polish Traditions.
2. It's really not worth it to spend Legitimacy to keep a Polish monarch on the throne past the first one or two. You do take penalties to the cost of a lot of things when a foreign monarch comes to the throne, but that's balanced by how much less unrest from abysmal legitimacy you have to deal with.
3. Everybody wants Gdansk/Danzig. You can keep Brandenburg friendly for a surprisingly long time, but eventually, if they've already knocked out Pomerania, they will come after Danzig and Ostpreussen. And if Brandenburg doesn't go for Gdansk, Denmark probably will.
4. Relative to 3, letting yourself fall three military tech levels behind Brandenburg is a really, really, really profoundly stupid thing to do. Seriously, I was MilTech 12 to their 15, and they completely wiped out my land forces inside of a year, no survivors.
5. You're probably better off focusing provincial development on critical/profitable locations (Warsaw, Krakow, Danzig, Ostpreussen, Vilnius, Kiev, Yedisan, Riga) than spending monarch points to develop the entire Commonwealth.
2. It's really not worth it to spend Legitimacy to keep a Polish monarch on the throne past the first one or two. You do take penalties to the cost of a lot of things when a foreign monarch comes to the throne, but that's balanced by how much less unrest from abysmal legitimacy you have to deal with.
3. Everybody wants Gdansk/Danzig. You can keep Brandenburg friendly for a surprisingly long time, but eventually, if they've already knocked out Pomerania, they will come after Danzig and Ostpreussen. And if Brandenburg doesn't go for Gdansk, Denmark probably will.
4. Relative to 3, letting yourself fall three military tech levels behind Brandenburg is a really, really, really profoundly stupid thing to do. Seriously, I was MilTech 12 to their 15, and they completely wiped out my land forces inside of a year, no survivors.
5. You're probably better off focusing provincial development on critical/profitable locations (Warsaw, Krakow, Danzig, Ostpreussen, Vilnius, Kiev, Yedisan, Riga) than spending monarch points to develop the entire Commonwealth.