Let me recommend trying Larry Jennings's "Ambitious Classic." Basically, you do a couple of ambitious card moves with the full deck, then say something like: "There's too many cards."
So you pull five cards out of the deck (say, the ace through five of spades) and do it with five: You push a card into the middle of the packet (and show it explicitly going into the packet), but then suddenly that card appears on the top of the packet. But there's still too many cards, so you set one card aside and do it again with four cards. And so on. As you eliminate cards, there are some variations in the presentation, and the mystery deepens. When you finally get down to the last card, you turn it over and the spectators see that it isn't one of the five cards you started with.
This is not a "packet trick" in the sense that any of the cards is gaffed. They are authentic cards that can be pulled out of a borrowed deck and the trick can be performed impromptu.
The moves are all pretty easy. The only one that requires quite a bit of practice to perform confidently is the block push-off.
