When I used 16c, I noticed something.
One might be silly and wait to get enough mana to upgrade 3 grades with 16 gems, put them in the box on the right and wait until one has enough to cleanly combine.
This is unreasonable and inefficient. An efficient way to upgrade while playing is to constantly do pieces of the upgrade and put the resulting gems in amplifiers or traps.
You have a grade 5 gem to start with 32 c, then you upgrade to.g8,g11,g14, up to g 32 before you slow down.
Then you have longer and longer breaks between upgrades.
Once you get to g55, you can start by duplicating the g55, then putting it in another trap near the original amplifiers.
Then remember the upgrades for 16c and do it in pieces.
It is (2+1+2) +(2+1+1+1+1+1+2+2)
You can make the first part (2), while keeping a 1 in a trap. Just u upgrade after d duplicating. Then d duplicate twice, u upgrade one of them and you have the (2+1+2) part of the 16c.
Just throw it in a trap with barrage and have a 1 ready for duplication for later.
There's no real reason not to break it up this way. Keeping gems on the fiels gains mana, keeping them in the combine space is no real use.
Each u upgrade gains about 40% efficiency, and that means 40% faster upgrades. This may hold for 64c also, but I've never tried it, as 16c works fine.
Are there formulas for how much a 2+1 adds to specials vs a u upgrade?