I am struggling a little bit to get Gradle running with Elastic Bamboo. I would install Gradle on our mounted EBS-Snapshot. Then take a new one and afterwards add this as Executable capability to the elastic image config. Is this enough? Since normally (like this guide: http://exponential.io/blog/2015/03/30/install-gradle-on-ubuntu-linux/) you would also manipulate your profile - but this is located on the ephemeral EBS of the image...
Use this script (e.g. for Gradle 2.5):
mkdir -p ~/mnt/bamboo-ebs/gradle && cd $_
wget https://services.gradle.org/distributions/gradle-2.5-bin.zip
unzip gradle-2.5-bin.zip
Then take a new snapshot from the EBS volume and use this in your elastic agent.
Afterwards add "Executable Capability" to your image configuration with this as path:
/mnt/bamboo-ebs/gradle/bin/gradle
Now you can use Gradle as Command in Build plans and add the task name as argument - e.g. "build".