How to match this given circuit to a model for a simulation?
First start with the approximations
L = L1 + L2 + L3
R = R1 + R3
C = C1
R2 is too large to do anything.
The influence of C2 could possibly be somehow added in to the simple RLC model, but I would ignore it unless there is some specific reason to include it. Once there is a reason to include it, then there should be a way to calculate its influence on the outcome.

Ignoring C2, it looks like your resonant frequency is about 377kHz, and the Q is about 6.4. This is not a great match for a 1MHz source. I assume that your program is going to tell you how to tune things up to get your big voltage to light up the gas tube.

Take care with the high voltage and the bright lights! I know a guy who remembered not to touch the high voltage but forget about the sunburn.