Run the install on a single run command to merge the update and install. If you add more packages later, this will run the update again and install all the packages needed. If the update is run separately, it will be cached and package installs may fail. Setting the frontend to noninteractive and passing the -y to install is needed for scripted installs. Cleaning and purging at the end of the install minimizes the size of the layer.
FROM debian RUN apt-get update \ && DEBIAN_FRONTEND=noninteractive apt-get install -y \ git \ openssh-client \ sudo \ vim \ wget \ && apt-get clean \ && rm -rf /var/lib/apt/lists/*