Not wanting to be overly confrontational, but my first bit of advice would be to disregard ROYm's advice. This is for several reasons. Showoff with Cards is rubbish, but it's not by Brian Tudor. His Showoff Volumes 1 and 2 videos (now available on DVD) teach some very good fundamental flourishes and shouldn't be confused with the aforementioned Magic Makers' product. The value of Showoff 3 is, I accept, more of a moot point. Also, the Clip Shift is not one of the most useful moves in magic. It's a nice thing to play with, and it's got a lot going for it, but in terms of general usefulness it comes well down the list below a double-lift, a false-shuffle, a shift, a side-steal, a top palm...and so on, and so on. Also, although not to my taste, I've heard good reports about several of the Ellusionist DVDs, especially the Ninja ones.
Personally, I would recommend buying a good old-fashioned book rather than a DVD. If you haven't got The Royal Road to Card Magic, Expert Card Technique and The Expert at the Card Table, then get them. However, if you've already got them, you could go for Drawing Room Deceptions (which is sold on Dan and Dave's site, and is therefore cool).