So, me and my gf have an hypno kink, but although I consider myself to be a pretty ok dom we want to use some videos or tapes for a bit of roleplay and stuff like that, any suggestions?

Hit up the various hypnosis themed reddit communities. Some are RP, some are for actual hypnosis. Regardless of which you want, you can probably find some material by asking around.

also be careful, carefully review any material.
while most of us are all right, some try to go through shady methods

Depends on what you two want. I know there's a lot of readily accessible bimbofication material, but I'm not too familiar with female sub material as a whole. Nimja and Vive Hypnosis are two names that come to mind. Nimja in particular has a "Hard Reset" file that can be a good way to make a clean break from past hypnosis. I've used it a couple times and it works nicely.

I would recommend using EntrancementUK videos. Lex is an expert hypnotist, and provides training for inducing trance in a subject. Most of his videos use real hypnosis. While TheSecretSubject has plenty of good how to videos: www.youtube.com/watch?v=Ob-CWqEbETs.