Practical history for writers

Revising Auroradawn, I've realised that although I'm dealing with Great Families - a type of nobility really - I didn't know very much about their history.

So I'm having to invent some for the rewrite.  I've decided that the families are the descendants of key specialists who came to Vedrana with the original settlers.  I've assumed they were already quite wealthy when they arrived. 

Each took land and created their own family estate.  I've imagined them building big houses, and adding to them over hundreds of years, rather like England's stately homes.  

That bit was easy,  working out the planet's government was a bit more tricky.  The Great Families sound like some kind of feudal arrangement, but I don't like the idea of them ruling the population like lords. I'm a fan of democracy, imperfect as it is. So I've decided that Vedrana's going to have a two-house system of government rather like England's, with an elected Assembly and a Great Council made up of  the Great Families,

So far, so good.  Now I need to decide why each of the Great Families settled in the locations they did.  In the original novel (which is over ten years old) I just dotted them around the planet's different continents.  Some live in alpine areas, some temperate climates, some tropical, and one in an Arctic region.  When I looked at it again, it was obvious that they chose areas which corresponded to their homelands on Earth.  The people who settled were diverse, some dark-skinned, some light, so it made sense for them to settle in climate zones they were comfortable in.

I'm not naturally a fan of history, so I do only what's necessary for my story.  I need a kind of practical history for writers, one that doesn't go into lots of detail of the past, but lays out broad trends.  "Because of this your ancestor did that" is the sort of history I'm after.

I'm not going to need a lot of this detail for book one, but I'm writing a trilogy and I think I might need it by the time I get to book three.  So it's back to the history drawing board now.  What occupations did my Great Family ancestors have?  I really must decide.