Also I just learned a bit about the Doryani’s Institute Lens. Apparently you can get a level 19 gem to level 21, and a level 2 enlighten/empower to level 4 which would be huge. You can get +2 levels, you just can’t go past 21 or 4. So all those times I didn’t put a level 20 gem in I could have taken a chance with a 19 which I do frequently have sitting around thanks to the dying anguish divination cards.
Researched it a bit and there’s plenty of conflicting opinions which makes sense given that fairly common outcomes will be things like +1 level and -1 level appearing to do nothing etc. There are enough reports of the same outcome happening twice though that it seems to be correct. I wouldn’t waste a level 19 gem you wanted to use on it, but if you’ve got extra 19s around and nothing better to put in there it might be worth a shot.