There isn’t much to the connection between Ruby and SDL. It is pretty
simple and straightforward. You’d do better to join an SDL community.
There is lacking documentation to some of those projects. Some people
on the list proposed to write better docs, we emailed the author of
Ruby/SDL to ask him to set up a wiki and he never replied. It didn’t
go anywhere from there.
If you need specific help on how the bindings work, feel free to email
me or the list.