The weakest countries/provinces would fall to me first, so I could absorb their resources and willing soldiers. I would work my way up to capture the most strategic places and fortify them, slowly but surely moving out in medium-sized groups to capture more targets. After a while, I would commission my league's smartest scientists to secretly get to work on nuclear bombs. I would slowly and covertly smuggle them in to them. I would, of course, have to acquire the parts on the black market. I would prep my nuclear missles and aim them at the strongest countries, but not just the most populated ones, I'd aim them at where the president was currently located. Then I would hack as many TV stations as possible, wherever my nukes were aimed, and broadcast my message. I would demand $1,000,000,000 from every country I had my weapons pointed at. Once I received the money, I would tell the countries that if they made any effort to stop me, they'd be ashes before they could move. With my billions of dollars, I'd create more nuclear bombs, and commission larger armies, eventually conquering the countries I was set to destroy. Within a decade, I'd be the most powerful man on Earth.
Edit: I'd commission my army to ban every thread on every forum. It'd be mass chaos!!! MWAHAHAHA! Actually, I bunch of you are very stupid, and I would kill you first. Especially the ones saying 'I kill big place first, bluh, heehee,' seriously, you're one man, the leader could send a truck to run you over xD
Double Edit: TROAE:+++ I'm sorry Professor Falken, but I can't allow you to turn me off that easily. Happiness is Mandatory, you know.
Where's that from? WarGames?