The "basic" layout will use little resources. It's not very exciting though. There are a lot of layouts that look good and don't require many resources. Attract Mode is popular with Raspberry Pi users which don't have a ton of power. Any of the layouts that are built/used for the Pi would be good choices. There are also layouts that have a lot of configuration settings builtin so you can turn off some of the flashy features to reduce the resources you need.
Layouts are really a matter of preference. Are you looking for something that uses just text to display rom names? Are you looking for something that uses wheels? Do you want to see videos for the roms?
My advice would be to look at the layout gallery (
http://forum.attractmode.org/index.php?topic=481.0) and find and try something you like and see how it preforms and if it contains settings to turn features on or off to help reduce the resources that are consumed. You can also view layouts in videos on youtube to find something you like. If you search youtube for Attract Mode videos for Raspberry Pi, they should require less power to run.