Originally Posted by Cantu
Well I figured it out myself so I think I should share.
You get the town
Demolish other government
Military Occupation
Migration
Pastoralism
then...
at least nomad market
at least settled community
at least warlord's horse herds (IMPORTANT: If you build reformed pastoralism and don't have this one you will no longer have access to it, or settled aristocracy for that, preventing you from getting the reformed government. If you messed up already demolish reformed pastoralism, then migrate again, build pastoralism again, and then get your herds)
Reformed Pastoralism
Advanced Settlement (kills settlement)
Settled Aristocracy (kills herds)
...
Reformed Parthian Government (enables MIC and other cool stuff)
Hope that helps you (and anyone else).