As an alternative if you have a lot of PP spells: Don´t bother with any guest race buildings except the Portal.
I think it was about 700-800% for the entire chapter.
Chapter 13 and 14 I by far the best choices of chapters to spend all your PPs on. Those two guest races take forever to play with buildings, but can easily be completed in a month (or two weeks if you go nuts in the tourneys) using PP spells.