I've seen gifs and pics of real people on here so I was wondering cause I was thinking of doing a hypno manip of a cosplay pic. But just to be safe I was wondering what are the actual rules about that.

You can read the rules for posting here by clicking where it says Rules in red above or the link below.
hypnohub.net/wiki/show?title=help%3Arules_and_policies

But to answer your question directly, from the site rules:

Real Photo Manips
Manips of real photos and images are not permitted.

the only stuff with real people allowed is stuff that's already hypnosis related from the source.

The main problem with this is that, like with say Kisekai, you can easily use automated software to create a literal ton of decent quality content. It's not even bad quality, which could easily be taken down with quality control, it's a decent quality flood, which would kinda drown other sort of art. Real life content that depicts hypnosis is of course fine, as is picture manipping, which does generally take a fair amount of effort.

Now of course you can't generalize that. There are Kisekai pieces where a ton of effort was put in, and if that effort is noticeable then it will be permitted. There can also be real life manips that took a lot of effort and not just a combination of an eye finder and a spiral insert, something an AI can do today. On the other side picture manips can be just as low effort, although the worst are taken out by quality control. But generally manipping pictures and especially creating original art just takes so much effort compared to computer generated real life manipping and other computer generated content that the latter are banned.

That's not the main problem. We have other rules and a Quality Control team to deal with issues of quality and mass produced images.

The main problem with manipping real life images is an issue of consent. If you've ever been to an Anime/pop-culture convention in the last decade you've probably heard the phrase "Cosplay is not consent".

Since there is no reasonable way for the website to know whether the people in the real life images consented to the manip (and we can't really take the poster's word on it), it's better to not allow any of them