There is no
targetSdkVersion of 24, nor is there
compileSdkVersion of 24, at this time. Those will be valid values (presumably) when the next version of Android ships.
For the N Developer Preview, based on my work over here, use:
buildToolsVersion '24.0.0 rc1'
You also need Gradle 2.10 or higher (see your
gradle/wrapper/gradle-wrapper.properties file or your standalone Gradle installation) and
'com.android.tools.build:gradle:2.1.0-alpha1' (see the top-level