I'm a fairly new trad leader so I have a small rack: BD Stopper 4-13, C4's 0.5-3, a bunch of slings, plenty of biners...

I'm hoping to do Story of O in a month or so and wanted to see what else I might want on my rack. I don't have a lot of cash to buy gear at this point, but I want to make sure I'm well covered. Is there any natural pro on the route?

Seems pretty well photographed on Mountain Project.
There is a video of someone climbing Oldtown which is fairly nearby on the precipice.
https://www.youtube.com/watch?v=VexE5wlhEFc
That said I've only been on the Precipice trail myself and Otter cliffs.