Which 6k card to chase (CL: 20k)

nearly series 4 complete, but missing out on a lot of series 5 cards, so i want to chose wisely with the next 6k.

what card from these would you recommend for being fun, maybe even archtype necessary or just strong?

aurora

dormammu

elixir

fenris

galactus FS

goliath

man-spider

marvel boy

sage

stardust

toxin

weapon h/x

zombie cap marvel

zombie mr. fanstastic

missing a lot more, but those would be cards i rarely (never) see in the game, so i guess they are not worthy 6k with the above missing also.

thanks for any input.