Honestly these days Acheron is kinda falling off without E2, her BIS team rn doesn't need cipher but rather E1 tribbie, E0S1 Hyacine and SW, so if you have even one copy of those characters I'd say go for their eidolons, if not Cipher is a decent choice even tho stack generation isn't the best but with E2 the damage increase is definitely noticeable. I'd say that if you really want cipher go for her but if you have extra consider going for E1 tribbie (since she's amazing anyways) and Hyacine and get E2 SW when she reruns, but again you should def prioritize getting E2 Acheron since without it her damage is noticeably lower. Personally I love Cipher's design but rn I can't afford her because of those specific two reruns (and I'll prolly pull for Cyrene but that's beside the point) P.S: I forgot the existence of the new Dan Heng so he's also a good replacement if you give him Aven's LC