I pretty much settled on the standard gem sizes because redoing all of the gems is a PITA. I changed the spellgems to vertical and reset the numbered background. I fixed the floating target and casting windows.
I changed the icon offsets on the hotbar xml so the gems look better. I set hotbutton windows 3 and 4 to look like 1 and 2. If you don't like it I can make them all vertical like it was but with smaller buttons so that the spellgems actually look better.
You can grab the whole UI from
here. I would suggest you make a new UI folder for this and try it out with /loadskin.