Admin sections are a part of most applications that one builds. Usually we lookup to active_admin for a quick solution. It is pretty straight forward when you have to do a few simple configurations and the dashboard. If your project is big and as the models start increasing plus if you need to do anything that is a little complex; it all starts to fall apart. The code becomes very hard to manage and maintain. So, it saved you the initial effort for the admin section but it brought its own set of problems.
CHOOSING A RIGHT GEM FOR YOUR ADMIN SECTION
There is another way you can be quick and the code will be clean and maintainable. The gem is inherited_resources. This gem actually helps you keep things clean, flxible and maintainable. I would strongly recommend taking a look at it before using active_admin gem.
Just a side note you could also use the inherited_resources gem in your regular controllers where you have your standard actions and want to add more to it. The readme has detailed information about its capabilities. You can find it here.