Oh, and also, hot-air balloons (I know the basics, I know where to get natural gas, and knowing the basics, with trial-and-error, I could produce an invaluable scout - the French used the balloons in Franco-Prussian war especially, to report enemy movement; The Prussians invented a special AA cannon to combat the balloon, as guns and bows did not have the range)

Then I would make a compass and discover Americas. There I will attempt to create a secret Roman Empire, so in case the Old World one falls, the New World one remain safe for a time being. I will keep it secret to deter any Columbus-like individuals. And I will spread the myth of horrific dragons and monsters in the Atlantic Ocean to scare-off future explorer. I may even bring a stuffed anaconda to illustrate the example, or dig up some dinosaurs to further frighten the people. Also, there I will go to Chile and discover the immeasurable bat-guano deposits which will create a fantastical agriculture.