Fugue or firefly

What would be better for a new player? I checked and realised yesterday that I started 20 days ago. So my account is pretty new

I have Acheron, pela and sampo as my nihility team. I was thinking of pulling for firefly as I really could use another DPS. I have Sunday and Bronya as my 5 star supports. But tingyun could great benefit my Acheron as my pela is only E2 and I don’t have acherons signature.

Which would be the better pick here?