New player need some buying advice

Hey all,

I am just getting into the game. I've watched several videos, but they all recommend things that I can't find anywhere.

So far I have the Core, Green Goblin, Captain America and Black Widow.

I can't find RotRS, Sinister Motives anywhere. No cyclops or wolverine.

Curious with $200 what you would recommend me getting? Feel like I need a campaign to get going. Amazon.ca has sinister motives for $60, but seems pricy compared to Mutant campaigns, but not sure which one to grab and what else to go with it.

Hoping to take advantage of some boxing day specials.

Appreciate any help and Merry Christmas to you all!