What were Joseph Stalin’s dreams and ambitions?

More than anything else, Stalin wanted power. And as he was such a ruthless individual, he was prepared to do anything to attain and hold on to it. He proved himself remarkably devious and manipulative in getting to the top of the Soviet Communist Party despite concerns among rivals about his personal manner and intellectual ability. Yet Stalin showed incredible audacity and cunning in elbowing his rivals to one side in his quest for absolute power. Once he'd achieved this ambition, he then set about systematically getting rid of them and anyone else he perceived as a threat to his total control.
Stalin's biggest rival was Trotsky, one of the undisputed leaders of the Bolshevik coup of October 1917. Stalin resented him for a number of reasons, both personal and political. There was also a radical difference between their respective visions concerning the future of the USSR. Trotsky believed in the doctrine of permanent revolution. This meant that the long-term stability and success of the Russian Revolution depended on revolutions breaking out in neighboring countries, which would then lend the Soviet Union ideological, strategic, and military support.
Stalin, on the other hand, advocated "Socialism in one country" whereby the Soviet Union would consolidate the Revolution by a rapid process of industrialization, enabling it to compete with the capitalist powers. Stalin was committed to the belief that there would be a permanent condition of ideological warfare between the forces of capitalism and communism and that the Soviet Union needed to prepare itself for this by building up its industry as well as its armed forces. In doing so, the USSR would fulfill one of Stalin's most deeply held ambitions: that the Soviet Union should become a major player in international affairs, challenging the United States and the other capitalist powers for dominance and control in certain key strategic locations such as Europe.