If I start near volcanic regions, I try to take them all since they are very easy to protect and very hard for the AI to invade.
Every time I get 400k to spare, I install a factory upgrade, at least two so build time is reduced to one for the Hercules but often I go as far as five. Once money comes rolling in, I switch to Achilles production, and a little later to Hercules production. Mercury cyborgs that are not needed for fortress manning are used to build capitals in the remaining interior regions. Important frontline regions also get tier 1 fortresses. Once I got enough money, I start building Mars cyborgs continuously and send them to the frontlines. Along the way, I check each region they move through for the income value and if it's above ~10k, I build a capital there is funds allow it. I use them to quickly move towards the nearest cities since they give the most credits.