In my first book, the characters travel from south to north along Khriza, their homeland. But in the sequels, certain characters (and eventually all the characters) travel outside Khriza. How do I handle cities? Since they aren't discovering the cities for the first time (they're not explorers or anything), how do I handle cities that pop up on sequel maps that went unmentioned in the first book? Should I just plot out every city in my world? That seems like it will clutter the map a bit. Though, my dragons aren't ones to put their cities all together like modern humans. Cities are usually about as far apart as one can fly to them, sometimes closer in certain cases.
I assume you're planning to include the map with the story? I don't feel like that's necessary, and not doing it would eliminate the problem. Though you could also just leave it vague - the first map only shows places that are visited or mentioned in the first book, subsequent books follow the pattern.
Seems to me like you can go two routes: 1) Map out everything of relevance in the 1st book and ignore the rest--you can come back to it later, or 2) Map out literally everything, and rest assured that everything will remain in its proper place. I'll tell you what, though--I took the second route for my story world, and holy damn is it a time investment. The plus side is that I know where everything is and can make myself chuckle by having characters reference cities that exist. The bad news is that readers don't honestly care because it isn't plot essential ._.
This is the route I see usually advised - with the added proviso of focussing your worldbuilding on the main character and what they see. For instance - If your main character is the village blacksmith, and gets sent on a journey down the dark path in the wilderness, it's probably not worth it to worldbuild the court intrigue and high politics beyond what impacts the plot (you can, but it's non-essential). On the other hand, since the character in my scenario is a blacksmith, it probably WOULD be worth the details to know things like smithing techniques, how common iron is in the world, where iron is obtained, and any magical or weird details that might affect the day to day activities of a blacksmith. The closer something is to your character, the more you need to know.
Even if you don't include the information in your story, or on the map in your book, I suggest you do a rough map just for your knowledge. I wouldn't spend a lot of creative energy making it pretty, its just to aid you in your story plotting and relieve your mind of having to remember those details when you have it spinning in creative mode.
A good example would be the map at the front of the recent fantasy novel The Traitor Baru Cormorant by Seth Dickinson. There's a big world with a sea in the middle of it - the main character is from Taranoke, South of the sea, and probably the opening quarter of the book is set there. Her homeland is conquered by Falcrest, West of the sea. However, the most substantial chunk of the novel takes place in the province of Aurdwynn - North of the sea, where the main character is stationed a Imperial Accountant. He wrote an entire blog post about how he designed this map, why it is what it is, and what he purposefully left off. The map at the beginning of the book is only of Aurdwynn - neither Taranoke nor Falcrest are marked at all, other than by arrows indicating their general direction. Taranoke vs. Falcrest is the emotional angle driving the whole book, but neither of those places come into play geographically. Aurdwynn, frankly, is just the chess board on which that bigger conflict plays out - but it's also the only place in the book where the geography and high politics are relevant. Personally, I think this map was a master stroke, as a lot of people would have done a world map including Falcrest and Tarnaoke, but then you wouldn't get the necessary detail on Aurdwynn, which is what really matters to the plot.
On your signature... What are you talking about? I start sentences with d*mmit sometimes. But only when I'm mad enough to use moderate profanity.
It's just a quote I thought was funny from Aaron Sorkin about writing dialogue. It's from a promo he did for MasterClass. It's a bit of an overstatement but actually it did help me refine my own dialogue because sometimes it can be overused in ways that don't match natural speech unless you're Dr. McCoy from Star Trek, for whom it was a character quirk ("Dammit, Jim, I'm a doctor not an interpreter!")