Since you seem to like the make it easy for you way, here you go. An easy way to take advantage of other people's work is to go to the DesktopX Widgets Gallery and type "meters" (no quotes) in the search box or click the
WWW Link. I have a favorite one here Blister Pack
WWW Link.Sysmetrix can display ram usage but, whether it does, depends on the theme author. If the author included ram usage in their theme then Sysmetrix will show it. Sometimes you might have to check the theme with your mouse to find it because of the theme design. That should get you started in the right direction. Just go to the Sysmetrix theme gallery, download and install a few and have fun.