There is a standardised way to cite ancient authors in academic works based on how the work is divided. This is because every well known ancient work is divided into the same way, at least if you're using a proper version made for academics, and not just for popular audiences. If you don't have a version like that, I recommend Perseus Tufts online. This is so that no matter what version or translation you have, you can still easily look up the same section when you come across the citation. You never write pages if you can avoid it for ancient books.

In the citation, no matter what style you're using, you write a shortened version of the author, the shortened version of the name of the book and then the citation that the book uses. For example, The Republic by Plato is divided into books and sections. So the very first part of the book would be cited something like this:

^(1)Plat. Rep. 1.327a

So, you're almost correct in the way The Gallic Wars is cited. It divided into books and chapters. However, you need to put a short form of the work in question, even though it's probably clear in the context you're using it in your video. Caesar didn't just write that, and there were multiple authors called that, so I would write:

^(1)Caes. Gal. 4.15

In the bibliography (if you have that), you write the full information in the way your citation style dictates. Remember to include the year and translator/editor.