Spending hundreds on a piece of software you're rubbish at using doesn't sounds like a sensible idea, but then if you're willing to pay someone to tell you what Google can then I assume you're not exactly short of spare cash!
I think what you might be missing is the correct keywords in your searches though - although you're right that actions are your best route.
Looking for "batch watermark photoshop" or "bulk watermark photoshop" brings up loads of tutorials that tell you how to arrange it in different positions.
While slightly out of date this looks like a pretty good tutorial that even mentions the pitfalls of trying to process landscape and portrait images:
https://www.youtube.com/watch?v=hI49P5D_n5s