I've been running her primarily with Seismic Claws, because it's fantastic and flexible.
Is it wrong to answer with Arcanist upgrades in the TT forum? >.> I've been playing with Imbued Energies (killed: get 4 cards; discard to gain fast) and Philosophers stone (SS+flip to get Wp/Df increase; discard to get 2 cards). Fast on Mei just lets me abuse Seismic Claws more, and the Philosphers Stone gets me some quick defense for a bit, and then on the turn I gain Fast I draw another 2 cards to help get those Tomes and Masks rolling for the Tiger's Claw triggers!
I played with Thunderous Smash once, because I wanted to be able to deal with Scheme Markers better, but I didn't get to use it at all in that game...so it's back on the chopping block.
I'm not certain about Vapormancy. I feel as though, if I'm that close that I have enough other options to choose from.
Price of Progress looks pretty good, but whenever I have the choice between having a 7SS cache and taking PoP, I seem to have the extra SS...so maybe I value it less.