Build questions

Hey guys,

Last year some friends and I made a little set-up in my yard. Nothing huge, all we had was a
-4 foot drop in
-box
-flat rail
-circle rail (no idea what the technical term is.)

I would show some pictures, but my camera's broken.

I have the tools, space, wood, and pvc for some more stuff, any ideas?

Also, I live really close to a college with plenty of handrails perfect for some urban. Anyone know how I can build a portable drop in for around 50 bucks? The one I have right now is too heavy.

All help is appreciated, thanks.