Make videos on what you personally are interested the most in, and maybe make different series’s, like solved/unsolved cases, serial killers, mysteries, disappearances, etc, also find some more unknown stuff cause people dont really wanna watch 10 videos on the same few cases. Most importantly tho: Keep it interesting, and not so dry. There‘s tons of channels that just report on the facts, but in the end personally, it‘s the personality of the channel owner that keeps me interested. The comments, the personality, your opinion, maybe even humor etc. Theres a reason buzzfeed unsolved is so popular haha
Looking forward to ur channel, i hope you‘ll post here if you start one!