[thejeff]

You don't have to wait. I've never been quite sure whether it's more effective to boost taxes at once and get as much as possible while pop is still high, but lose more to unrest, or to tax more lightly while the province is still producing a decent income.
The key to the income producing sites is to drive the population to 0 so you can double tax without unrest.

You do also want to build temples to push your dominion. You're not actually going to get castles & temples in every province, just as many as you can.

You may just not be expanding fast enough. In SP, growth should be pretty explosive.