Thor > Yondu > Scarlet Witch > Corvus > Ironman = Medusa
A great premium card is more important than any one uniform imo so definitely get the card.
Get Yondu because you like him and he's fun to play.
Scarlet Witch has more use than any other of those characters so it'll help you more.
Corvus is very good PvP character with the uniform. If you play AC or don't have any other metas to play TL, it's a great choice.
I put Ironman pretty low on the list because even tho it's a great uniform, he doesn't shine on any end-endgame stuff.
Medusa gets a good boost too. I just bought her uniform and didn't play much (and she's very underbuilt too) but it seems way better than her original.