Do you play card games?
I'm just curious.
I play Magic the Gathering, and Hearthstone.

Only Magic and Battle Scenes.

The only one I've tried is Hearthstone, but my temperamental connection makes it impossible. I frequently suffer short disconnects, that's just long enough to automatically lose an arena game. Naturally that doesn't go to well with the fact that you can only lose three times in the arena, and you need to spend gold to enter in the first place :P
Still, I enjoyed what little I could play of it a lot.
Magic seems even cooler, but I'd imagine it requires a bigger time investment.

Hearts is pretty cool as well :D

And money for the boosters.A lot of money for the boosters.

Been playing Magic for some time, but that didn't last very long. Now I'm looking into Warhammer 40k Conquest and am playing a ton of Dominion with my wife.

My GF plays a lot of Pokémon. Those virtuals CCGs like M&M Duel of Champions seems pretty nice.
But Thank you for letting me know that there's a 40K CCG.

Lots of money and big time investment? Nah, then I'd rather get into tabletop stuff, like 40k and battletech :P

You know what they say:"crack is cheaper"

If you're starting with a F2P account, play casual/ranked. You need some cards from the classic set (like Azure Drake, Defender of Argus, Big Game Hunter, etc), and unfortunately Arena doesn't let you select classic pack as reward.

Perhaps, but come on, this is awesome: I tried, and perhaps I'll try again one of these days. My internet connection has been more stable lately for some reason. Still I was kinda put off one day, when things were going well in a casual game, until the other guy dropped Deathwing on me :P

If that makes you feel better, Deathwing is rarelly used, since it doesn't clear the board, most of the time (minions with deathrattle are very popular, like Harvest Golem, Piloted Shredder, Sylvanas Windrunner -> steals the dragon :p), you have to destroy all the cards in your hand, and pray that the opponent doesn't have some form of removal. It's a bad card.
About the internet, have you tried playing Hearthstone in your phone, Matewis?

The problem with Hearthstone is that I need to drop money on it. And I already do that with Magic and Battle Scenes.

I haven't no, but that is a thought. However, my phone's connection is not all that great either sadly, at least not where I'm staying at the moment. I often have trouble open websites with it, so I don't think Hearthstone will perform any better on it.

It depends on what you want to accomplish.
If you want to get legendary card back, for example, you don't need to spend money, there's lots of cheap decks you can copy (netdeck) in hearthpwn. One of the most hated, Face Hunter, can be used to go to rank 1, and it's very cheap. Unless you don't have patience/time to get gold, it's doable.