I'm unpublished, and never wrote a book before. With that said....
If you want to write a series, you should understand tricks authors use.
1. Chiastic structure (also known as chiasm or ring structure) is big for resolving issues invented in earlier books. Rowling used this for Harry Potter. George Lucas used this for Star Wars. It is used quite heavily for series.
https://en.wikipedia.org/wiki/Chiastic_structure
2. Gustav Freytag's dramatic structure:
https://en.wikipedia.org/wiki/Dramatic_structure
Note: Your novels can follow the Freytag's structure by placing them, in a grander scale, on the same pyramidal graphic.
There is much more to understand. You can do what I did and research for 6 months. I think searching through this forum is another viable option to learn some of these tricks. I think the two I named are absolutely critical for writing series.
My timeline is 25 years, set in 3 eras. There are breaks of at least 2 years between each era. Each era follows Freytag's structure with chiasm. I won't write book two unless book one sells. If it does well, I have lots to write in the future.
For you, breaks between books are up to you. It depends on how your story goes. Your chapter one, book one, can be world building and introductions. Chapter two can pick up many years later. Book two can do the same thing, or it can immediately pick up where book one ended. It depends on your story, chiasm, and so forth.
I'd wait for others to post, but these are points I would like to share on your topic.
Good luck. Writing a series is a daunting task, and it takes a lot of commitment.
Are you thinking a trilogy?