Build structures that make units (Barracks, V. Factories, etc.), then have each
of them to make units. For example, if you made two Barracks and told one to
make fifteen soldiers and the other to make fifteen soldiers, both barracks will
make them. This works for both IPC and GHOST. This trick will allow you to make
soldiers and attack a lot faster.
The best map is Sardines as you can build more on there. A good trick is to
build all the newest things that comes out. However this will require a lot of
money, and some of the new things you unlock are useless. For example, the
planes, spies, commandos, subs, boats, advanced things, doctors, civilian
helicopters, and grenadiers.