You're going to need a lot of liberty bells.
Unfortunately, Elder Statesmen are very expensive (1900 gold), and you need a University to educate them. Immigrants who are Elder Statesmen are, as you might expect, very rare.
So use other means - use free colonists and colonists with useless specializations to work as Statesmen, build Printing Presses and Newspapers, and get Jefferson and Bolivar as soon as possible. Note: getting Bolivar early may be a bad idea. He gives a one-time bonus to all existing colonies. If you're planning to expand, hold off on Bolivar until those colonies are up.
Buying 1 Elder Statesmen is often necessary (so he can teach others). You may even want to buy a second one, but it's probably better to invest some labor in building a University early.
If you have a few Statesmen, think about using them as a "Bureaucrat Rapid Reaction Force". If you quickly need to increase your support in some colonies, put one or more Elder Statesmen on horses (see "the fundamental rule of colony management"), and move them to those colonies, then put them in the state house.
Bells accumulate in colonies (there's no such thing as Rebel/Tory colonist, only Rebel/Tory colony). 200 bells are needed per unit of population to get full support (without Bolivar).
So if you have accumulated 800 bells, and there are 10 colonists in a colony (2000 bells required for full revolutionary support), you will have 40% support, that is 4 Rebels and 6 Tories, or 60% support (6 Rebels, 4 Tories) with Bolivar.
The number of bells required for each founding father grows in a regular pattern, except for the first one.
- Viceroy: 56, 225, 225+112, 225+2*112, 225+3*112, ...
- Governor: 48, 193, 193+ 96, 193+2* 96, 193+3* 96, ...
- Conqueror: 40, 161, 161+ 80, 161+2* 80, 161+3* 80, ...
- Explorer: 32, 129, 129+ 64, 129+2* 64, 129+3* 64, ...
- Discoverer: 24, 97, 97+ 48, 97+2* 48, 97+3* 48, ...
So total cost of the first N fathers on Viceroy is:
- 1-5: 56, 281, 618, 1067, 1628
- 6-10: 2301, 3086, 3983, 4992, 6113
- 11-15: 7346, 8691, 10148, 11717, 13398
- 16-20: 15191, 17096, 19113, 21242, 23483
- 21-25: 25836, 28301, 30878, 33567, 36368
On Governor:
- 1-5: 48, 241, 530, 915, 1396
- 6-10: 1973, 2646, 3415, 4280, 5241
- 11-15: 6298, 7451, 8700, 10045, 11486
- 16-20: 13023, 14656, 16385, 18210, 20131
- 20-25: 22148, 24261, 26470, 28775, 31176
On Conqueror:
- 1-5: 40, 201, 442, 763, 1164
- 6-10: 1645 , 2206, 2847, 3568, 4369
- 11-15: 5250, 6211, 7252, 8373, 9574
- 16-20: 10855, 12216, 13657, 15178, 16779
- 21-25: 18460, 20221, 22062, 23983, 25984
On Explorer:
- 1-5: 32, 161, 354, 611, 932
- 6-10: 1317, 1766, 2279, 2856, 3497
- 11-15: 4202, 4971, 5804, 6701, 7662
- 16-20: 8687, 9776, 10929, 12146, 13427
- 21-25: 14772, 16181, 17654, 19191, 20792
On Discoverer:
- 1-5: 24, 121, 266, 459, 700
- 6-10: 989, 1326, 1711, 2144, 2625
- 11-15: 3154, 3731, 4356, 5029, 5750
- 16-20: 6519, 7336, 8201, 9114, 10075
- 21-25: 11084, 12141, 13246, 14399, 15600
For a population 100 empire (only colony population, no soldiers/pioneers/etc.) you will need 200 * 80% (Bolivar) * 100 = 16000 bells. That means about 16 (18, 20, 22, 25) fathers just as a side effect of building revolutionary support. Unfortunately most of them will come late.
There seems to be a pattern:
- The first few fathers are cheap, so they come quickly
- Then you build industry, but have no (or 1-2) Elder Statesmen, and only a few Printing Presses/Newspapers, but they are much more expensive now so they come slowly. Jefferson helps in this phase.
- After you build a University, the number of your Elder Statesmen skyrockets, you probably have enough Printing Presses/Newspapers, and the cost of founding fathers grows only slowly, so they come quickly again.
The cost growth is linear, so the relative growth is very fast at the beginning (the second father costs 300% more than the first, the third 50% more than the second, the fourth 33% more than the third), but small at the end (the 16th is only 6% more expensive than the 15th). On the other hand your growth patterns are more like exponential (each doubling of liberty bell production takes approximately as many turns).