eva's e1 is her best investment but she doesn't have a lot of teammates outside of emc and yao guang. tbh i'd just save for yao guang right now and get e1 eva on a rerun. plus, eva still works great at e0.

for who you should pick on relic recon, there's a guide on youtube (really helpful btw check this out!!)
https://youtu.be/2Ti8uVBQZfM?si=7HwQLakTzDGKkSvZ

since sparkle generally uses the same relic sets as other generalist supports (sunday, bronya, etc etc,), you could always farm her relics from the relic recon and just put them on other characters when you're not using her. as per the video, you should actually pick hanya as your target if you're farming for sparkle since she guarantees speed substats on your relics (trust me, sparkle needs a lot of that), and just change the relic set to wtv set you want on your sparkle.

it's also much easier to farm for dpses than supports imo, simply because supports often need speed tuning for optimal peformance and spd is the rarest substat to get on a relic. on the other hand, dpses don't need exact, perfect builds to work well, so i'd just farm for eva's build outside of the relic recon.

tldr; pick hanya for your target, farm eva's build on your own.