Ok, now the trick, how to crank out grade 11 gems (you can actually get grade 13's this way):
Make SURE you have a steady mana growth, depending on fluctuations I say you want at least 140,000 MP.
Then click Ctrl-tab 3, and click grade 6 Gems.
Now hold Ctrl and click combine tab, then click on a gem, repeat several times until it's all done, this results in a grade 11.
To get a grade 12, repeat once.
To get a grade 13 keep going but you have to pay attention because
at some point you will have two 11's and a 12.
Not sure if you can get a 14 this way, by the time I get a 13 I deploy it then build another to stack on top of the deployed one, giving me the 14.