Panic farm for R2

Okay so r2 is coming back way earlier (fk was planning on palp coming back to get 7* palp) so who should I panic farm and which lead.

I’ve got two choices magma or rg (0/85 so really going to have to invest in rng)

I’m looking at tarkin/Vader lead/tfp/st.

Vader I need 4 shards st is 91/100 and top is around 30/100 will invest fleet whenever he pops up