Anybody working with Gradle for Android should take a look at Gabriele Mariotti's collection of common tips for Gradle. He's assembled two sets of tips (part one and part two), and each covers a fairly wide range of topics, complete with explanations and code snippets. The tips don't get too advanced - many focus on organizational suggestions, for example - but address a lot of common issues that even more experienced Gradle users may run into, and the question-and-answer format gives it the feel of a kind of unofficial FAQ.
It should be noted that these are not tutorials to help you get started - Mariotti does point you to a couple of helpful ones, though - but tips for people already working with Gradle, particularly those who are relatively new to it. So, if you've run into problems with Gradle or want to pick up some tips to keep things working their best, check out part one and part two of Gabriele Mariotti's Gradle tips.