Faustus claims he will use his powers to rule. He will travel through the air and unite Africa to Spain by a bridge to make the people of Africa tributaries and increase his power. He assumes he will already be the ruler of Germany. He wants to unite the world but only to rule over it. His motives are clearly base and self-interested as he never mentions how he will use his power to improve the lot of mankind. He is obsessed with self-aggrandizement.
Marlowe's theme seems to be that power easily corrupts when placed in the wrong hands. Once Faustus gets the power he squanders it on showing off to impress his social superiors and to mock his perceived adversaries, much as any unworthy man might squander power foolishly. Faustus lacks the character to handle power with restraint and to use it for good. Because of this he fully earns his damnation.