Hmmm world conquest you say? Sounds pretty interesting so i'll take a crack at it.
First of all if i ruled the world i would assemble a massive army of highly trained soldiers. Then i would hire scientists to create large suits of armor, like the one's you see on Gundam Seed and the likes. After they manufactured about 1000 of these, i would get my best soldiers to control them. They would be my strike force, attacking rebelling countries and assisting ones under my command. As for the rest of my army, i would manufacture hundreds upon thousands of APC's, Tanks, jets, helicopters(attack and transport), battleships, submarines and in due time i would install a humongous laser orbiting the earth. It's blast radiuis would be the area of affect a nuclear bomb would make only three times more destrcutive. But i am a benevolent ruler, and i will use democracy and talks of peace for other countries to join me. Any who refuse or rebel however, will be dealt with swiftly and mercilessly.
As for economy wise, i would fund different ways of improving our soceity such as cheaper non-gas powered cars, more use of solar, wind and water power, a highly trained police force to deal with troublemakers and i would create home distrcits for homeless people, give them a good education, and i would let them aqquire a vast sum of money beofre asking for payment back. In my own continent of North America however, i will not ask for taxes. Other countries would provide that. I want my continent to be the best educated, most lethal, strongest and overall greatest in the world. Am i starting to sound crazy? Yeah probably.
However, although i am a benevolent and just ruler, i will not tolerate intolerance for my rules. If a neighbouring country refuses to yeild it's arms war with another or myself, i will destroy them. If they continue to rebel i will destroy their cities, burn their land and enslave their people. The people will then be forced to work, not labour work but jobs that noone wants such as space station obeservation or latrine inspectors and cleaners. As or their land, i will make it either into a weapons testing sight, or if it's still alive, i will give it to a neighbouring country.
Overall, yeah i think i could handle the world. The only thing is will it remain after my death? Or, like the mighty Roman empire, will a empire destroy everything i have worked so hard to create? Guess i'll never know...