I actually have a google doc started on court! It's something I was writing to help someone else, I'm starting up on court behavior but it covers who was in court so far, and how they'd get there. I have a couple of my babes in there for name examples but the method holds true
Bookwise I recommend
Machiavelli's The Prince (Basically a How To about ruling a country)
The Dragon Riders of Pern Books (Not in medieval times or even court but McCaffery shows a good idea of how they handle ordeals within a kingdom, Dragonquest and Dragonflight are my favorites, but Ruth the White Dragon is about a lord holder)
The Wrath and The Dawn is set in a Middle Eastern Court and does a good job showing the intrigue
Historywise
The Medicis are a good choice to research, they're not royalty (by blood) but they played politics well, they're like the real life Lannisters
Anne of Cleves was one of Henry VIII's wives, she pretty much won at getting politics to work in her individual favor
Wu Zetein Climbed from Consort to Empress
The Chinese Consorts are suprisingly well documented, like you can find what food they were given by rank so I totally recommend looking at them.
I'm not an expert, but my mother's a Tudor history buff so I've picked up how court works (mostly in the renaissance) , and I do obscene amounts of research before I do historical things.
Oh and btw at least in the 1500s
Russia- Basically the black sheep of europe, they're very different from everyone else
Eastern Europe is really conservative after they become protestant (which is early 1500s) they're generally behind the times because they're away from the other major courts
Spain- Was undergoing the reconquista in the medieval era, it wasn't united and I'm betting no one's calling it spain
France- Is the fashionable court
England- Is 2nd best
Slavic Nations- Yeah I have no idea what these guys were doing.
I don't know who you're working with or what changes you've made that I'd need to anticipate but that info might be useful
Also helpful
-This is a timeline of food if you want to make sure things are historically accurate, remember Europe doesn't have corn, tobacco, potatoes, chocolate etc until the 1500s. Lots of people make that mistake when it's so easy to avoid.
http://www.foodtimeline.org
Here's a tumblr post on the language of fans, it was mostly used in the Victorian era but in a fantasy setting if you're not using real countries it's a useful tool to use with ladies in court (Idk if it'll give you the post or if that picture's it but hey, I tried)
http://perchancetodance.tumblr.com/post/68854381807/hottiesinpurgatory-faeryhearts-in-the
And finally this is the language of flowers, now the meanings can be different depending where you reference but this is a great tool for sending messages. I know Shakespeare uses it in Hamlet (Ophelia's speech is great if you understand what the flowers mean) but I don't know exactly how old it is.
http://www.languageofflowers.com
If you need any other info I'm happy to help that's just what I've got from the top of my head.