General

There is a lot of weight gain encouragement content on YouTube, coupled with a ton of feeding videos as well

I listened to the Horngry podcast two years ago. It features one fat admirer (the woman) and one gainer (the man, older so with some more experience in the scene).
It can be pretty random, and the intro music is really... something. But overall I recommend it. It did enought to keep me interested, and they both seemed down to Earth.

Here's a link to the first season on Youtube:
youtube.com/playlist

(The 2° has many more episodes, but each one shorter)

There are some great BHM’s with YouTube channels about weightgain, doing chugs, q&a’s, things like that. My faves (in terms of quality and quantity) are: Robert Frankton, Daniel Keaton, and WadeGain. AmiFatYet only has a few but they’re excellent and boy is H U G E. And then there’s this one, which is a stand-alone on this channel but if you ask me it’s *chef’s kiss* top tier:

Also there are some “hypnosis” channels that do weight gain encouragement, rapid weight gain, and trances where you expand rapidly, transform, experience breast expansion, etc. My faves among these are Silver Hypnosis and Lady Harleen Hypnosis. For either one, they have a wide spread of content so you have to do some sifting, but they’re fun. Hope you find something you like.

All of what Quiver said, + Studmuffintop & Vin. I really liked weirdwood (or Woods is Weird). She was on YouTube but I think she does a podcast now.