I'm just starting out, myself. But I get ideas by reading social media and seeing what people are talking about. I also look at what others in my niche are doing, and seeing if I can put my own spin on it. One of my fave YouTubers recently released a video which was exactly the same concept I had planned to start working on. When I commented on it (that I had wanted to do the same idea), he replied with "everyone tells a story differently". I thought that was awesome.
Basically, I guess what I'm trying to say is get inspiration from other YouTubers (don't copy... just be inspired!).
Good luck.