You can think of this website as an "onion" or "rabbit hole" that begins on the front page. Here, there are some very large topics, such as "writing" and "reviews" that you can select from, or a collection of links to random, interesting content. These pages, when young, end with themselves, and go no further. However, as they grow, they gain a navigation bar to content further in. This process repeats over and over again, leading you deeper and deeper into the webways. Or, you can think of it as a growing and branching tree.
I think, in general, it is best to avoid saying things like "this website is under construction" because you can show this with your actions. For example, by making use of indicators like NEW or FRESH it's easy for me to signal that the website is being constantly updated.
I also think that it is a mistake to comment within the page, "in the future I'll do this". In the environment of NeoCities, this kind of a thing is understood. Outside, it looks unprofessional. And at a personal level, you will likely forget you ever even wrote that and won't update it when you actually create that feature in the future! I think it's better to link to a skeleton page.
Because static pages take actual human effort to update, and sometimes a lot of it, I think that it's generally the correct idea to link to a skeleton page, and write as if it already fully exists and is well developed, because in the future it will be. You have to think about the maintainability of it all. Do you reasonably think that you'll remember to update every page that references the pages you hadn't created yet?
You should, of course, check pages and update them as frequently as your schedule allows, and that's how I use my maintenance log. I use it to make sure that I check in on and update my pages methodically, for both style and content. The truth is that when you build things quickly, your ideas change and mature over time, and your skill improve.