. . . and build churchs, large churchs, monasterys, and Templar houses.
A build strategy, however, should be done smartly. Hold your powder, don't go willy-nilly building the above structures until they are really needed because they reduce the intake of gold.
If one already has a few hundred piety, there's no need to build churchs. But, if the ruler is new, and/or piety has slipped into negative territory, then that's the time to begin a massive bulding program.
Templar houses are something of an exception to the rule, where they not only add piety but also troop levels. One may need extra troops on the frontiers, in which case the Templars come in handy.