What processor images to install

After downloading and installing Android Dev Studio and Android SDK, a question arises:

Which System Images should one install?

For example, one would like to write a simple android game, that should be run mostly on mobile devices (e.g. pads and smartphones). I guess in this case most many Images are not needed.

Is there a good way or routine on how to choose which System Image to install? So the system is not over-flooded with unused tools.