I'm trying to get a PR reviewed and it's going nowhere. I'm asking on SO to see if anybody here might know, is Filterrific still being worked on? There are a few PR's, lots of issues, and the author has yet to respond.
I am using filterrific gem myself. I have also experienced bad respond on issues & seems like the author is not so active himself.
Gem authors are also not obligated to give support but if they do its always a plus.
But to be fare author himself has used a lot of times to create good documents. At first when I was setting up the gem, I also had issue but if you read his documents carefully (read here), you will understand the most.
I also recommend you to take a look at his demo app source code (found here)
By looking at the codes you will always set together stuff to create your own scope.
You can also follow all questions related to filterrific gem on SO (here)