I doubt anyone on this site is familiar with conjuration or even believes it is possible. The closest thing you might get is transmutation, which is the conversion of matter and most related to alchemy. Conjuration on the other hand, which is the creation of matter, is theoretically impossible since magic obeys the laws of physics as well. While E=mc^2 does open up the possibility that matter and energy can be converted back and forth, creating even a single gram may require an enormous amount of energy (that can't even be calculated since magic is so variable) that is hardly worth the result.
One purely theoretical possibility is that you could reduce the energy cost by making it so that the matter you create will degrade back into energy after a certain amount of time. Keep in mind, however, that this is a completely untested theory and there is no known method, to my admittedly limited knowledge, of accomplishing this. If you are determined, be prepared for a long haul of spell research and practice.