Relying on Google ad-sense may not be your best bet. You could look into other ad networks, or even selling your own ads privately; but a better option, in my opinion, is to look into publishing your stories in a magazine instead. A lot will pay you for first-publishing rights.
I have never looked into doing this for horror stories, but I quickly googled "horror short story magazine" and got quite a few results, including this list on Medium
Getting accepted can be difficult though. I submitted a few times to sci fi and poetry magazines like Neo-opsis and Arc and was always rejected. Just remember that doesn't necessarily reflect the quality of your writing and not to be disparaged. You could be rejected for any number of reasons, like how much space they have available in the upcoming issue, the editor's personal taste, or maybe they prioritize known authors.
To address that last possible reason for rejection, you could try publishing somewhere for free at first. There are sites like Creepypasta
or you could find a horror-themed wiki. Or, if you're a college/university student, it's very likely the English department has its own student magazine. Although I agree the concept of working for "exposure" suuuuuuucks, getting your name out there as an author can be an important first step.
There are a lot of hurdles, but if you're looking to make money from your writing I think it's better than the ad-based approach.
Oh, and if you do publish your stories anywhere, definitely let me know. I'd love to read them.