>>536015419
3 here is literally the only key you need. Sketchkin is the best support outside of some V3+ limiteds so it won't be wasted. Purples are also like 1 core/key.
V6SF should be your top damage from just her counterattacks alone, ignoring her making TLL attack 3 times per turn. Have her S2 TLL on every odd turn and have her Ult on CD. Refresh TLL early if you would have to skip an ult (and if the ult isn't going to cap SFs CI giving her another turn). Any free turns should be S2 of Nikketa.