I'm new to the game so to speak but I've recently moved into the middle of nowhere and have some free time so I reckon it's time to build me a spud cannon. This will be my first so I have a few questions that will most likely be answered in other threads but I got tired of looking

I'm on a pretty tight budget for my first cannon, let's say $50
I need to know what the most efficient design would be within that price range and the minimum required parts for a BEGINNER spud gun.
If anybody could point me in the right direction of a thread or give me some design tips I'd love to knock this thing out in the next day or two.
Thanks again