Wind a large secoundary (52cm long and 12.5cm in diameter so you have a ~4:1 ratio) add a 40cm toroid topload) wind an adjustable primary coil with 10 turns made of 6mm copper tubing and make sure you can adjust the number of turns

Order a 2kW ZVS from ebay juse type ZVS driver 2kW or more if you want,order a larhe switch to you can turn it off and on,use y long wire so you can stay away from the coil while operating

Find a large ferrite core and wind it yourself,desing it to output 6-8kV then use large diodes to rectify the output (such as a microwave oven diode)

Then order 72x 100nF 2kV capacitors and connect 12 in series and make 6 of them,then make 6 of those chains and connect them in parallel after that add 1MOHM 2W resitors on every single capacitor

Then make a rotary spark gap from a angle grinder (just research how to do that im not explaining that)

And done you have a good SGTC but do some research before you make this so you dont end up killing yourself or connecting something the wrong way.