In addition to /u/cdesmoulins comment, I think once you have a grasp, whether basic or advanced, of a particular topic or period, you're inevitably going to start to want to looking into narrower questions. For me, in some of the periods I cover, there's not necessarily much value in reading the latest general history given that every general history over the past, say, 50 years might just be reinterpreting the exact same source materials for a general audience, and you might just want to find out what the new thing that warranted the book is or see if a particular issue is raised.

This becomes an even more pressing issue when you start getting into either multi-volume histories of a period or a series of monographs focused on narrow aspects of a topic within a period, etc.

So for me, when I approach something like questions on /r/askhistorians (not to mention in order to satisfy my own curiosity), I've become a great lover of indices, foot/endnotes, and bibliographies.

A good index is your best friend when you're researching a particular question, especially one that goes beyond names and places and also includes topics.

Likewise, you should find out what the major tertiary encyclopaedic reference works are for the field you're interested in. I, for one, feel quite lucky that the Enyclopaedia of Islam is as extraordinary a reference as it is and am really excited for whenever the third edition is completed, which I think is scheduled for the next decade or so. Other references like the inevitable Cambridge History of [X] are also invaluable. I refer to the Cambridge Histories of Turkey, Egypt, Iran, and the First World War very frequently, both for my personal use and here on the sub.

I also would highly recommend /r/askhistorians long-running Monday Methods series, which is just a really fantastic series on historical approaches, methods, research techniques, theory, and so on that has been very helpful to me personally as one of the non-professional-historians on the sub.

It's not dumb at all! What you're experiencing is a totally normal part of developing an interest in a specific historical era and everybody here has probably experienced it too. My first reaction when I'm interested in a period of study I don't already know a lot about is to hit up the library either for an overview or whatever else I can find -- if you're not sure where to start or are hesitant just pulling anything off the shelf not knowing if it'll be an interesting and useful read or not, the AskHistorians booklist might be a good place to start. I don't spot a ton of overviews on Byzantine history but there's at least one, and there's ancient Greece recs, ancient Rome, early and Imperial China, the Celts, the works. You can also search around through past answers on this subreddit and poke around in the sources people are citing for more reading material related to the specific historical topic at hand. I'm also a little embarrassed to say that this subreddit and its online resources list turned me on to the existence of Google Scholar, a tool for finding academic articles across platforms by keyword search, and in any given search query there's usually at least some that are completely open-access. (If you have access to academic journals through school or work, even better. Lots of public libraries in the US allow you to request articles from academic journals and take home a copy in print-off or .pdf form -- as an independent scholar who's not associated with a university I use that one a lot.)

You can read books that give a broad overview of a region or a culture and then make note of the stuff that piques your interest within that span, or dive in at random with a book or article whose topic sounds interesting -- I recently began a research spiral on urban 16th century Italy just because a presentation I read about had a cool name. As you read more you'll begin to develop a personal BS detector for bad history/bad writing, but you'll also learn more about which aspects of history interest you -- military strategy? arms and armor? philosophy? art? religion? women's history? material culture? -- and carve out a niche of stuff you find interesting. Nobody has to be equally knowledgeable and enthusiastic about all history to consider themselves a history enthusiast or a historian -- I know next-to-nothing about the American Civil War, for instance, and I'm fine keeping it that way unless it's historical material that overlaps with something I do care about like the history of sex or the history of mourning. Neither does anyone start off in history knowing everything about their topic of interest and exactly what they want to focus on, even people who go through grad school for history. I know "start anywhere" isn't especially helpful, but there's no wrong way to get into history and there's lots of possible places to begin gathering info about a topic that interests you in history.

EDIT: In addition to books, academics' blogs are often an amazing way to get an idea of interesting topics or likely reading in a field you're curious about. (And also to kill time.) I have no good recs for how to find academic blogs except by doing what I already do and googling around, but anywhere that cites specific sources can be a useful starting-place.