All religious traditions take guidance from more than just holy books (many religions do not even have holy books), and the idea (or assumption) that laypeople can determine religious truth by reading the holy book themselves is pretty much restricted to Protestant Christianity.

The fact that Swoopo promotes itself as an auction/shopping site and lists "strategy" as part of the experience skates uncomfortably close to the "no fraud" clause listed in that link, although offering discounts to losing bidders would seem to give them a solid "it's only gambling if you choose to treat it that way" out.

There are none in the Bible. The closest you get are exhortations about work, or warnings about pursuing money. Some folks extrapolate from there, but the arguments against it are always indirect. More often than not, they're not scriptural at all, but are based on practical wisdom ("It destroys lives! It's unproductive!") that doesn't have a lot of basis in actual practice.

It's not anything like widespread enough that you could say it was a "Christian teaching," though. While you can still find people who say it's sinful (and you will always be able to), it's getting so that standard Southern Baptist Sunday School materials say, "Is Gambling a Sin? Well . . . not reeeeeaaallly . . . but we don't think it's a good idea." And I think those guys are usually just about the last to let go of issues like that.

Not in the bible, but the talmud says that someone who "plays with doves [i.e. gambles on pigeon races]" is disqualified from being a witness (i.e. their moral character is suspect).

Gambling is considered a form a stealing since the person who lost doesn't actually want to give their money to you, they are forced to by the roll of the dice. In normal commerce you get something when you pay. (And don't say people enjoy playing, no one enjoys playing, people enjoy winning.) I believe, but am not sure, that lotteries are not considered as bad though.