It says my recommended number of corporations is 36 but, I am at 24. So I've built 6 additional corporations but ran out of workers around the 3rd one. Gold Coins or increase the salaries to bring more folks in?
Don't put too much value to the recommended number of corporations. I don't know why it's still there, because you can see yourself when your country can build extra corporations and how many workers you need to have a 100% hiring rate at the corporations.
As you increase pop, the recommended number goes up, so even if you did jack up your pop, you'd be chasing a moving target. Hitting the recommendation is almost never a good idea.
That said, increasing pop is good. Check out Aries' guide to C3 warfare and my guide to looting C3s, both in the beginner forum.