I always use in magic bicycle cards or phoenix cards so I have over 50 old used decks and I use those for practicing. I keep them all in a box so I can just grab them and practice. You want to use the same brand for practice as for performance so I just practice with my old bicycles. I also have a couple of decks that aren't used very much ( just a little worn ) and I use those as duplicates for performance. For example, I take the deck that I am using for performance, I add the duplicates from my spare decks and take out the real card, saving that for after the performance. I hope that makes sense. The idea is just to use your old bicycles that you don't use anymore for practice.