Build first in the capitol, then in other holdings then in cites and bishoprics. Get all holdings to level 2 before going on to level 3. Going beyond level 2 doesn't make economic sense becasue the ROI is over 500 years but it does help when they are military buildings for larger levies. When building new cities/castles/churches; base citites repay after 75 years. Base castles after 166. It does make sense to build monastic schools and universites for the technology increase. Buy in order:
  1. Paliside
  2. Castle village
  3. Low Wall
  4. Castle town
  5. Militia Training Ground
  6. Archery range
Warrior Cult
Stable 1
Stable 2
Iberian 1
List 1
Altaic 1
Rus 1
Stable 3
Wall 1
Barracks 1
Wall 2
Barracks 2
Train 1
Italy 1
English 1
Wall 3
Keep 1
Keep 2
Militia 1
Militia 2
Keep 3
Scot 1
Barracks 3
Balt 1
Keep 4
Barracks 4
Militia 3
Iberian 2
List 2
Altaic 2
Rus 2
Stable 4
Italy 2
English 2
Wall 4
Scot 2
Balt 2
Train 2
Keep 5
Barracks 5
Iberian 3
Wall 5
Rus 3
Italy 3
English 3
List 3
Altaic 3
Stable 5
Scot 3
Balt 3
Iberian 4
Italy 4
Rus 4
Keep 6
English 4
List 4
Altaic 4
Scot 4
Barracks 6
Balt 4