I have a persistent issue in which, I have an idea for a story. I sit down and I start that first draft, but a few pages in I realize I don't have much actual meat for the story.

When I try and come up with ideas to add to the story, I usually end up tossing the idea away cos it feels like I'm unable to expand it in a meaningful way.

For example:

I had the idea of an urban fantasy story. MC, Jessie, recieves a journal from his fathers estate after his dad dies. Journal details a lot of preternormal happenings and even some notes to help Jessie learn things.

I had the idea that Jessie would join something akin to Social Services for the supernatural beings of the world, and each story would revolve around him dealing with some major case while an overarching story developed.

But now I don't how to connect those story dots. Or add more characters without it feeling contrived and disjointed.

Am I missing something? Is this how it always feels? I've never been one to draft stories either so maybe that's what I should be doing? Any advice?