New Player! Any tips?

The best way to figure out what is and isn't good is to experiment. Definitely look around this site for ideas, but playing the cards and getting to know them will teach you a lot. What's good or not is also going to vary from character to character (and sometimes scenario to scenario), since all heroes are unique and some are better with certain cards or aspects.

Generally speaking, the campaign boxes are the best value for the money, and IMO Mad Titan's Shadow, Sinister Motives, and Mutant Genesis are all excellent. Rise of Red Skull is a little more straightforward and probably best if you're just starting out, though, and definitely save Galaxy's Most Wanted for later since it can be the most frustrating. Otherwise pick up your favorite Hero(es) or any other scenario pack(s) that catch your eye.

Welcome and have fun!

Welcome to Champions!

I second what @TonyStark said about experimenting, and I'd like to add a few tips. Usually, you want to keep "one-of" cards for upgrades and supports that you cannot have in play more than once (such as Avengers Mansion). I rarely put only one copy of an event card; if it's any relevant, one copy isn't enough to find it consistently.

Captain Marvel thrives on (using her "rechannel" ability, Photonic Blast, Energy Channel...). Knowing that, i'd suggest you keep as many as possible and cut the rest. I'd suggest taking 3 Relentless Assault, 3 Haymaker (even though it's considered a bad card, here you use it as fuel for Captain Marvel) and 3 Emergency. Make room for it by cutting Uppercuts, First Aids, the two The Power of Aggression. Captain Marvel has lots of resources anyway.

You can find a few "Core Set" decks on this site too, from various authors. I did a few of those myself, not too long ago, if you want to experiment a little.

Last, Campaigns usually are the best investment. I think @TonyStark's suggestion are the way to go. Definitely not Galaxy's Most Wanted first! But Sinister Motives, Mad Titan's Shadow and Mutant Genesis are amazing.

Have fun!

Thank you @TonyStark and @neothechosen! That helped a lot! @neothechosen, can't "The Power of Aggression" be used as a energy resource? Or can wild resources not be used in place of other resources?

@Darth_Cluny

Yes it can! So you can also use it as fuel for "rechannel" or trigger requirements. So if you want to keep it it's entirely up to you, but I often refrain from including this many resources with Captain Marvel, only in case my hand gets clogged with resources and nothing else. You can test with and without to see what feels best.

Awesome @neothechosen! Thank you!