I was recently given a task to create a blog using Ruby on Rails. So I found a very helpful guide, which was very helpful for the blog. However, there seems to be a short supply of good Ruby-on-Rails guides on creating a wiki that is, up to date, makes sense and accurate.
You can check existing gems for wikis: https://www.ruby-toolbox.com/categories/wiki_apps
There are 3 rails-based wikis.
The most active is https://github.com/alno/irwi.
Other two, https://github.com/queso/signal-wiki and https://github.com/AndyMoreland/kii, was not updated for years, but still you can try to look through sources to get the base idea