For those who don't know and are unfamiliar with the Techno-Wizard, a TW is very different sort of mage. Think of him as a mechanic with an over-active imagination! Unlike most mages, a techno-wizard is actually inhibited by spell casting. And unlike an operator, most of thier devices really don't have a physical function. The idea being if it looks like it should work, than it will! Of course, it does require the spells that the techno-wizard had in mind as it's mystical function, but let's stick with the construction basics for now...
On first glance, a techno-wizard device can appear to be somewhat gaudy, and rather useless. Most often, it is actually an empty shell of a device that does not contain any moving parts that make sense. The outside of the item will be covered with copper wiring and circuits interconnecting various types of jewels, the kind of jewels required is determined by the spells needed for the item. The device also needs a "trigger" of one sort or another to activate it, much like the use of a toggle switch or an "on" button. If the item is a weapon, a trigger becomes more than just an analogy.
The look of a TW item is also determined by the specific function of the device. Obviously, a gun will look a gun, while a means of flight might not be so cut and dry. Some may create a jetpack-like item, others might create a pair of enchanted wings that attaches to their armor. It all depends on the nature of the techno-wizard and the extent of his/her imagination. As long as the TW believes that it will work, the device will work. Belief is just as important to the Techno-wizard as with any other mage.
A Techno-wizard can spend anywhere between hours and days, to even weeks and months building a construct. It all depends on the nature of the item, and the level of the spells need to power it. High level spells require more time and crystals to finish creating. A good resource to use as a reference is the Stone Masters magic in "Rifts:Atlantis", or the Gem powers in Heroes Unlimited as suggested by Jason Richards in the Rifter #2.
I would also suggest checking out the "The Techno-Wizard Extraveganza" in the Rifter #2 for more background and insight into the TW. Also, you can check out my buddy Mark's website, one of the co-writers of that terrific piece of work!