Well, if you buy the randomized packs of cards I kind of think you're being taken for a ride, but hey it's your money right (to spend at least, I don't know if you earned it)?
No, it's not evil. You can trust me on this. I'm about as right wing as they come, even around here, and I've got a copy of the Malleus Maleficarum hardly out of arm's reach of my computer chair.
Tarot, ouija boards, etc. are definitely evil and you should stay far, far away from them. Magic the Gathering is just a strategy game built around a somewhat dodgy but obviously lucrative business model. And good on you for buying a card from the secondary market... at least you know what you're getting!
A lot of this comes down to a fundamental confusion that I think people have about things and signs of things. Signs are important, and some signs are obviously things in themselves as well as signs. But we cannot lose sight of what thing the sign is in itself.
Here's the classic example, La Trahison des Images by Rene Magritte:
Take a look at that. The words say "This is not a pipe."
What does Magritte mean when he says "This is not a pipe"? It sure looks like a pipe. But step back for a moment: what is the definition of the thing you are looking at? The thing you are looking at is not a pipe. The thing you are looking at is a picture. That is its most basic definition. That is what you do with it, too: you look at it. You see, if it were actually a pipe, you could stuff tobacco in it, smoke it, etc. But you cannot do anything like that with it. This is not a pipe. It's a picture.
We generally figure this out when we're growing up. You have a Teddy Bear. When you're a child, perhaps you very adorably treat Rupert as if he were "Bear: Subtype Stuffed". But that isn't really true! Rupert is not any kind of a bear at all, and has no actual connection to Ursus. In reality, the amusing childhood mistake is an inversion of the true state of affairs... Rupert is really a "Stuffed Toy: Subtype Bear".
Likewise, Magritte's treacherous pipe is not a "Pipe: Subtype Picture". Rather, it is a "Picture: Subtype Pipe".
Here's another fine example: consider trips to Rome. You can have an expensive trip to Rome, a long trip to Rome, a pious trip to Rome, etc. Some trips to Rome can be several of these at once. There are all sorts of trips to Rome: religious trips, business trips, sightseeing trips, etc. But what about "imaginary" trips to Rome. You don't need a passport for those, do you? That's because an imaginary trip to Rome is not a kind of a trip to Rome! It's a kind of flight of fancy, one about Rome as opposed to being about something else.
So... what is Magic: the Gathering really? It is a game where you put out cards on your playing field that give you certain expanded options in the game, with a view to depleting your opponent's points before yours are depleted, etc. It really has nothing to do with actual wizardry... the game could be about corporate takeovers (Wall Street: the Geckoing), World War 2 (Normandy: the Invading), the Norman Conquest (William: the Conquering) or just about anything else. The game has a theme, and they seem to tie some of the mechanics of the game to that theme so that it is more fun to play, but really the pictures of ogres and dragons and so on are just there to entertain you while you blow up your opponent's hit points.
Contrast this with vile, sinful Tarot cards which are actually employed to try to ascertain the future with the aid of nebulous spiritual powers. They are actually used for divination, a sinful activity. Whereas in Magic: the Gathering even if you play the "Dark Ritual" card you don't actually perform a dark ritual! You just get some extra points to allow you to play that Skeleton from the Ray Harryhausen movie.
Obviously if a magic Skeleton Swordjockey ever appears and starts swording people, consult your bishop immediately.