Since this is under the category of "Anime/Manga", I'm presuming your asking what type of commentaries you should do relating to anime & manga? Personally, being a fan of Anime/Manga, I'd just do suggestions or reasons why you enjoy said anime/manga.
Though I'd be careful about it, Anime and Manga youtubers can have it rough. So I'd just suggest doing something like reviews about what you watched, but play it safe!