In the early game, you generally want to have many priviliges, because the minus absolutism doesn't matter.
The monarch points priviliges are great, if you're conquering a lot of different faith land then the interfaith dialog privilige is amazing. Minus advisor cost is always nice, etc..
Having a lot of priviliges also allows you to keep your estates above 60% in loyalty and influence, which gives good passive bonuses. You want your crownland to be 30-40, becasue at that level you don't get any maluses. Having high crownland doesn't give you much before the age of absolutsim.
After the age of absolutism, you want to get high crownland (iirc above 60) for more max absolutism, and repeal the unimportant priviliges until your max absolutism is above 100.