I've built a few 'nixie' clocks, one has an IV13 linear neon bargraph, they take more power than the average nixie.
There are 2 approaches, 1 is power them direct from the mains as vintage equipment often did, and the other is an smps, 100 tubes is going to use at least 100watts, so I'd be looking at a push pull converter, probably a sg3525 smps ic, and a etd39 or etd44 ceramic transformer, a couple of mosfets and the required dicretes, push pull mode without feedback would be adequate and simple.
Do you have much experience with switching supplies?