What is practical magic? What makes an effect, method or gimmick "practical"?
The "Old Guard" as it were, will preach all day that certain aspects of a trick are only practical if they are "worker" material. Okay, what makes something worker material? It kind of sounds like an excuse to do sub-par magic due to the lack of sleight of hand. It isn't practical if it cannot be adapted, changed, reformed and worked into the magicians repertoire with little practice. There are so many excuses out there, and they are all tired and lame.
If you need a gimmick to promote efficiency, that is fine. Do not make the mistake that gimmicks should replace true skill, they are there to make the magician's job easier in certain applications. Now, this does not mean you can be lazy because there is a contraption doing all of the dirty work; that isn't magic, that is science and engineering. The whole point of a trick or routine is lost when the effect is based on something a machine does, and the method can just be bought without needing to practice anything; this is even more true for something that can be accomplished with sleight of hand and lots of practice. Do not cheat your audience because you will just be cheating yourself.
"A quick note on practicality, is the root of the word, practice. If you practice something, you can make it practical. You have to put in the time to make it work for you. If something is not practiced, it sometimes is disregarded and labeled impractical." - Cameron Braxton
How can gimmicks be practical? Well, personally I feel that it should fit in your pocket, and be small enough to palm in/out of play. There are many larger things that can be used, but explanation will probably be needed as to why it is there, and what it does. Adversely, It is not very practical to due grand stage illusions like sawing someone in half, in a walk-around setting. So, moderation is key here. What works for you or me, may not work for someone else. If someone has a really good trick, but requires lots of set-up, they must use their own discretion as to if the juice is worth the squeeze.
One key thing here is, the practicality should not dictate the magic. If you are in a setting where you can use things from that environment organically, (i.e. in a bar and using a coaster, napkin, straw,) then at that moment, it is the most practical thing to do. Presenting a deck of cards somewhere cards are not typically found, can still be practical. Cards and coins are everyday objects that people are familiar with, so having them in a non-organic setting is not super off-putting. Bringing a close-up table while wearing a suit and tie, may not be the best idea for a beach or public park. Maybe, just maybe, that could be a gimmick in and of itself? Dibbs on that idea.
So far, we have touched on the practicality of the magic and how it can rely on the organic-ness of the objects, the familiarity with the objects, and the setting in which it is presented. The essence of what is practical depends on reading the situation, and knowing your strengths with certain gimmicks or moves. Do not rely solely on devices and contraptions to fit the setting and your performance. You are creating the set, the setting, and the presence of that moment. Create something beautiful, something impossible, something no one has ever dreamed of; if done well, that is what makes a moment truly magical.