Blessing - not bad grim, got recently buffed Alvein - useful as single copy, if you go to lawtia level 4+. His open works similar to Consuming Grudge, but it doesn't cost SP and no dmg. His ss is good too. Panther Soul - great grim to give units like Apprentice Knight or Ronin Girl rank up Vordore - he is worth using in a specific file, but requires 3 copies.
I think the best choice would be Panther Soul or Alvein.
Panther Soul is overrated. Why pay 1 permanent sp to rankup a single unit when you can play a unit and rankup every unit?
Blessing seems like it would require a dragon knight to maximize it's effectiveness, so I'd probably advise against picking that as well.
Alvein seems like your best pick, I can't think of any other unit that has it's effect on open. Could be useful as tech, but if you don't play a file type that increases lawtia lvl to at least 4 (or that has good SS to activate), you wont use this card all that much; however, f you don't have any use for any of these cards atm, Alvein will probably be the most likely to be useful in the future.
As a new player you probably wont have any use for Vordore, much less a single copy.