Here are YouTube video notes on two methods to get GPUs up-and-running for Tensorflow on Google Cloud. A quick one using pre-built Jetware instances, and one from scratch using a VM.
For either approach you need a credit-card enabled GCP account even if you are using free credits. You also need to change GPU Quotas to allow for at least one GPU. In the search bar in your Google Cloud Platform. Enable the GPU you want for your region. Click "EDIT QUOTAS", fill the form and wait for Google's green light.