Recently bought a small Tesla Coil kit via Amazon. Less than US$10. It is a simple one transistor flyback circuit (self-driven). It has a power FET if one wants to modulate the Tesla "arc" with audio. I haven't tried that.
The "arc" is pretty anemic with 18 V of Vcc. (I am using a power tool 18 V lithium battery pack, as I am concerned that the RF might damage my bench power supply.) I can light a CFL lamp from about 6 inches away. Will try to take a photo soon.
Next experiment is to take the coil (350 turns) from another Tesla kit and glue it to the original coil, connecting in series. I will put some RTV over the junction to prevent corona. This may overload the switching transistor, but I will give it a try. The primary is only one turn, so I will try for a 700 : 1 step-up ratio.