The constant things I always buy are 4 heavy oil, and 200 plastic. I usually get 10 miners, electric furnaces, and level 2 assemblers. Once I have power, and coal gasification up and running for plastic/explosives/batteries, it's just a grind.
I've settled on using an Island terrain, to give it an end, rather than just not wanting to keep expanding forever. Once the island is cleared, and has radar, it's time to start again.