Building a Tesla Coil
The problem with MOTs is the voltage is too low to make a sparkgap work reliably. A pair is just-about doable but still not ideal. A neon-sign transformer is an easier and safer transformer for a first-time coil. 
Insulation and /or spacing 
A ground with a low inductance path, and one that will not damage anything if it sees a HV discharge to it. i.e.  not the ground pin on an AC outlet. Stake in the ground is ideal as long  as the cable length isn't very long. 
You won't need to do any measuraments on the HV side. You will know if there is HV present - corona hiss, ozone smell, arc-overs etc.