Also, have your formers start forests in the squares you're not harvesting. They could come in handy if you need a place to expand to. An economic victory requires an element of obsession. Cash flow is everything. Basically, you have to put yourself in a situation where you have a large, productive territory that you can defend, so that you'll never, ever have to take offensive military action.
Wars cost too much money.
At these settings, however, don't expect to be able to send any units out into the world without throwing their home base into chaos. Instead, build clean units and keep them on alert in your bases, so they'll activate themselves if an enemy gets close. Building Priorities Resist the temptation to pump your Economy rating at the expense of Labs. Build facilities that enhance your economy and stability, ignore facilities that don't. Instead of building a bunch of vanity facilities that don't do anything significant to help you reach your goal, set bases that already have everything they need to work stockpiling energy.