While Cyanogenmod 12.1 allows you to customize most of your Android OS and brings a ton of additional features and apps that replace the original Google apps, the well put together apps from Google are irreplaceable.
If you install CM12.1 or older version of Cyanogenmod by default it doesn’t come with Gapps (Google Apps) installed these Apps include: Play store, Gmail, Maps, Google Backup Transport, Car Home, YouTube, Google Search, Google Voice Search, Google Music, and Google Docs. If you have experience installing custom ROM’s you will have no issue installing Gapps on Cyanogenmod CM12.1
Bellow, you can download GAPPS 90.6MB which include the Minimal Edition signed Google Apps for Android 5.1 which work with CM12.1
On CM12.1 older Gapps versions are also compatible like Google Apps for Android 5.0 Lollipop. If you are experiencing issues with the latest GAPPS for Android 5.1 you can always download and install these:
Bellow is a list of Addons for Android 5.1 Lollipop Gapps based ROMs like Cyanogenmod 12.1