If you have friends that play and have complete decks, my advice is play those decks for a while and decide if you really want to get into this game. I'm not saying you shouldn't it's a fantastic way to meet new people and have loads of fun, but just make sure you really want to put down the cash it's going to require to play.

If you DON'T have friends that play, my advice is go My Beloved like some other people were mentioning. Yes, Fizzle and Alfred are nice, but you don't need them to run the deck. My Beloved is a pretty good deck for a beginner, as it teaches you game mechanics and strategy pretty nicely.

As Mr. Prosak said, Avengers Reservist is probably the cheapest deck in today's meta. Mansion is literally the ONLY rare you have to play, and it does rival most of the big teams in character stats.

But, beware it doesn't teach you the real 'mechanics' of the game. Normally, you don't want to set characters as resources. But if you really want to save money, play Avengers Reservist.

Hope I was helpful.

Thanks for all the advice everyone. Since my local shop sells pretty much everything, I am going to first mod up my GK deck, since it seems easy enough to do, and am gonna try to build a Lantern Corp deck and probably an Arkham Inmates deck. Again, thanks for all the suggestions, and I'll definitely look into the Avengers stuff, despite the fact it sounds a little wonky.

EDIT: Oh, and how are Team Superman decks? They seem like they might be a little tough, since almost every character has the same name, so it seems like that'd restrict your field.

With TS, you use Superman<>Red's ability or Cadmus Labs to make them non-unique, so that you can have several characters named Superman on the field at once. That being said, they'll still lacking something.

I'll be honest, Team Superman is a terrible team. The new Superman in JLA made them slightly better, but they still are nothing near tier 1. However, TS is fun to play casually, especially with Longshot/Lost City for power up madness (but Kang Council is better at doing that since he's already non-unique.)

Basically superman needs a scarlet spider type effect for people named superman, and they also need something that makes cosmic worthwhile. Something as simple as an ongoing plot twist that is a team superman/(enter random team here) team up that draws a card and gives all characters with cosmic counters +1/+1 would do it.

Ah, cool. Thanks for the clarifications. And one more question... would it be worth my while to set up a Titans deck?

There were many cries of Titans being dead becasue Null Time Zone completely nukes their strategy. However, two TT decks made top 8 at the last $10K, so apparently they are not dead. It's an expensive deck, and hard to play, but it does pay off if you get good at it.