Keep in mind that your national cultures share the country's overall wealth with non-cultures.
And this can be a bad thing.
But also a good thing, if your pops are so ridiculously wealthy, that annexing foreign peoples can increase world demand for industrial goods...!
It's actually a disadvantage to Empire building. You might be able to conquer multiple continents but your national pops remain improvised and cannot purchase basic good and luxuries.
Likewise, you're also killing the world's economy as these conquered subjects (being twice as poor as your nationals) will be unable to afford things such as canned food and etc.
Keep in mind that your national cultures share the country's overall wealth with non-cultures.
So there's an actual disadvantage to playing as ''Empire''. Technically, you can play as a country and remain as L/F, using factory efficiency and population to build an economic empire. You can also expand your ''influence'' through alliance building, good relations and satelliting foreign countries.
It's something worth trying as an European or Latin American Republic. Just stay within your borders, use immigrants as craftsmen/clerks and attempt to overtake the U.S. as a manufacturing center.
Use your abundant industrial wealth to invest into Russia and Eastern Europe and get their resource production up and everything. You can also try to civilize the uncivilized world and thus increase their demand as well.