Fair use in geeky/Pop Culture blog

I have recently created a blog to review and talk about tv series, comic books, anime, merchandising etc and have been researching fair use for pictures. From what I've read, it seems that using a picture of the cover of a book or a promotional picture of a tv series/film/product in a review is fine. Please, correct me if I'm wrong. There are, however, two things that I haven't been able to figure out.

First, in the case of an item where there aren't any pictures that are clearly labeled as promotional, would using a picture from the official site fall under fair use? I mean, for example, writing a post about how much I'm looking forward to the release of a few things, among them a Pop Funko figure, and using a picture of the official Pop Funko site to illustrate the post. I've seen a lot of people do this, but I'm aware that many people doing something doesn't mean that it has to be right, especially when it comes to things like blogs and social media.

Second, my blog is completely for fun for the moment, but if I ever make any money with it, would anything regarding fair use change? I just started, so making money with the blog is a big if and I know that fair use can change, but I would prefer to do things right from the beginning instead of having to go through hundreds of posts to fix things in the future. From what I've read it seems that either the same rules apply or things are not clear.

Thanks in advance for any replies and I'm sorry if the answers are obvious. The more I read about fair use the more "but what if" kind of questions I have.

Sorry for posting from the wrong account before. I didn't realise a relative had logged in and not logged out.