So I recently got my hands on an IN-14 Nixie tube, Thing is I don't know what resistor to use.
The IN-14 Draws in 170v @ 2.5ma so 170/2.5 = 68kohm resistor but many people use different
resistor values so I'm unsure about what I should use. Maybe someone can clarify a bit?
Thanks.
The resistor corresponds to the difference between the holding voltage of the tube - which you say is 170 V - and the supply voltage which should be I guess, about 250 V.
When you know your supply voltage, you can calculate the resistance value. People use different resistor values according to what supply voltage they use. The supply voltage must be comfortably - at least 20 or 30 Volts - above the ignition voltage of the tube.
For This tube the ignition voltage is 150v so if I use a 170v power supply it should hold, is a 250v power supply necessary?
Well, this datasheet puts the ignition voltage as "no more than" 170 V, and I suppose the "hold" voltage may be around 150 V, so you would want about 190 to 200 V for a power supply.
I see, so if I use a 190v power supply then assuming the 150v holding voltage is correct and 2.5ma of current I should use a 16kohm resistor.
Sounds correct. 
15k is the closest common value, a quarter watt resistor should do just fine.
Great 
Thank you!