Start systematically acquiring gold until we have such a large supply of it that we can make loans to impoverished monarchs in the form of credit with our bank. We keep doing this for centuries and centuries until eventually we own nearly the entire world's gold supply and the government of every nation in the world is in debt to us. Allow nations to keep borrowing from us until the amount owed to us collectively exceeds the amount of actual money in existence, thus ensuring that every major power in the world will be permanently in debt to us. If anyone grows wise to our plans and tries to wage war on us, we get our puppet nations to gang up on him and tear his nation to shreds, and while we're at it fake a mass genocide and blame him for it, ensuring the solidification of our power by adding a burden of false guilt to the debt already owed to us.