My plan is a little complicated. I would hire a small force of mercs or find some like-minded people to help me overthrow the government of some third-world country that is too poor to adequately defend itself and whose loss nobody will care about. After establishing myself as king and making a constitution to make me look good to both my citizens and the international community, I'll start forming friendships with other nations and offer them cheap goods and services in exchange for helping me build up my infrastructure to a first-world level. Once everything is in place, I'll eliminate money from my country, replacing it with a full credit system that will ensure my people are well-taken care of and will allow me the freedom to research new technology at a faster rate than any other nation, without the consequences of debt. I'll use this opportunity to expand my territory into space by creating a reliable shuttle system and, hopefully, the first permanent space station on the moon, or at least a better orbital station than any of the previous versions. Meanwhile, I'll have been secretly producing the world's first space armada in a facility deep underneath my palace. Once the ships have been assembled and tested, they'll be taken apart and transported into space piecemeal along with parts for the space station, concealing their presence. Once all the pieces are in place, the ships will be quietly reassembled.
I will then purchase/create 1 nuclear weapon and detonate it at a safe location in the middle of the Atlantic Ocean, after sending messages to various news organizations so they can witness and film the actual explosion. Afterwards, I will send a recorded video of myself telling the world they have 3 months to give-in to my demands. After 3 months, I will randomly pick a city from among all the nations that have not surrendered and destroy it. This process will be repeated every 48 hours until everybody yields or the resistance is eliminated. Of course, the 48 hours are intended to provide time for people to evacuate; I don't want to turn the world against me because I'm a genocidal psycho. For every attempt they make to stop me (i.e. firing back), I will destroy a satellite, thereby damaging their economy and/or technical ability to resist.
My ships will come equipped with either a rail gun or laser weapons system for defensive purposes or local area offense (attacking satellites for example). For the city destruction, I will simply rely on multiple-warhead missiles instead of nukes due to their radioactive side effects. Plus, after the first nuclear explosion, the military will likely believe that all my attacks will be nuclear, so my barrage of multiple-warhead missiles will take their defenses by surprise, at least initially. Also, to help me keep world leaders guessing, I will only reveal ships as I need them. I'll start with my flagship, then when they try a larger-scale retaliation, I'll call in the others to provide additional assistance as needed.
