servo works when connected with usb but not with 9v reg power supply

I'm very new to electronics so forgive me. Will getting a another 9v reg wall wart, cutting the ends and plugging those into a breadboard with a voltage regulator work and be the cheapest/best option? If so, how would i go about sharing the ground with the arduino? Would i just leave the ground cable from the wall wart unplugged and use a jumper from the breadboard to the ground on the arduino?