Here's a Spell Gem mod I made by re-arranging Mafoo's excellent mod. The gems are the same size as the original Mafoo mod so they are easy to hit. The spellbook button is something I use so I enlarged it a little.

Below the Spell Gem window you can see my Hot Button window. I run a 1600X1200 resolution and these windows are both about 900 pixels wide.