Mike Turton has come up with this gem:
Using the map key “Rhaganeth” will produce Jauja with six diamonds and a gem in the province next door — plus one more in Huanaco on the other side of Cuzco. There are two more diamonds and a gem on the map in total.
Map key: Cernarduwys
9 Diamonds, 9 Gems total.
3 Diamonds in Mayapan (port included in the capital city), 2 Diamonds in Mul, 1 in Detroit, 1 in Iroquis (+ 1 in adjacent Uri) and 1 in Tlaxcala.
I played with France – 7 provinces:
Lots of sheeps (4 in one province), lumber, iron ore, 2 copper+ 2 Tin (one province has both), and 2 horses
My startup province was the SW (the province with two horses). First build an engineer and make roads with both engineers – to east to get the sheeps and iron and to northwest to get the lumber.
Send two ships to explore, to west to take Mayapan (with 3 diamonds) and to east to get Mul. I prefer on east first to take the capitol Carribia (4 wood, 1 lumber + port + cash). After defeating these two objectives send the ships home, or alternatively explore the whole world and take some capitol cities en route.
I left Detroit intact in order to colonize them. Detroit has 4 riches tiles (diamond, gold, silver and spice) so just buy these goods from them and they will soon join the empire. You can speed up the joining by purchasing other goods from them (cotton, sugar, tobacco).
My research priorities was to get Galleons (1542), Printing Press (1526), University (1570). Precious Stone Mining (1560) provided me with extra cash.
I developed Musketeers (1594) later, since I build extra Arquebusiers to conquer the natives.
Strong military prevents the other Great Powers to declare war early in the game. Later in the game I picked one by one the Great Power and expelled them from the New World. Even at 400 level, I managed to develop Field Artillery before 2 other Great Powers developed Heavy Emplaced Artillery, and quickly seized Spain. After developing High Grade Steel (Siege Artillery unit) in 1701, I destroyed Portugal and went on to England and Netherlands.
After capturing the capitals of the Great Powers (but not all the provinces) nobody will bother you. Finally, afetr capturing some provinces from sea, you can build up armies and in 1 turn you can capture all the remaining provinces from the old world.