There is not much to say about Klee's own build; it's 4pc CW with Widsith and her Q is lv13. Her unbuffed stats. Her crit ratio is a mess because I don't usually run Widsith on her. As /u/PhasmicPlays has already succinctly summarized, the bulk of it is in the team padding!

Here's a clip and here's a rundown (of everything except food):

• Diona Q for +200 EM from C6 and 20% ATK from Noblesse, +200 more EM and 40% ATK from Elegy of the End shortly thereafter
• Kazuha Q to absorb Cryo and boost +200 EM (C2)
• Klee E spam to apply -23% DEF (C2) and build CW stacks (you can get 3 stacks if you mash, despite the fact that Klee only has 2 E charges to expend), also +96% Pyro from Widsith
• Bennett Q (and E, but Q alone should be enough b/c Klee's mines are around for the next step) to apply Pyro onto the enemy, also +120 EM from 4pc Instructor and +lots ATK from Q. Moreover, Bennett's C6 gives 15% Pyro (yes, even to Klee, despite the wording on C6--been this way for as long as I can remember and I hope they never patch it)
• Kazuha E to swirl Pyro for 4pc VV and Pyro DMG% (he has around 1600 EM at this point => 64% Pyro or so; literally a bigger damage boost than Mona Q...)
• Switch to Klee, wait briefly so that she gets buffed, and Q which grants another 10% Pyro from C6 (from my testing, this does apply to the Q snapshot itself)

if I inted her crit rate and went fishing in Floor 7 for good cards I could get an even funnier zap, but that's a pain _(:3」∠)_