In 1600 the economies were estimated at :
China and India and other nations had larger GDP but it was Spain, Portugal, France, Netherlands and Britain that were the players in colonizing the Americas.
Region / Country GDP (PPP)
mill. of International dollars GDP Share percentage (%)
World 329,417 100
Ming China 96,000 29.2
Mughal India 74,250 22.6
Far East (excluding China, India,
Japan, Russia) 24,088 7.3
Africa 22,000 6.7
Spanish Empire 20,789 6.3
France 15,559 4.7
Italian States 14,410 4.4
Ottoman Empire 12,637 3.8
Germany 12,432 3.8
Russia and Central Asia 11,447 3.5
Japan 9,620 2.9
Eastern Europe (excluding Russia) 8,743 2.7
Spain 7,416 2.1
British Isles 6,007 1.8
It was not mainly about gold, it was about pepper. Europeans used a lot of it, and went to enormous efforts to get their hands on it.
Henry the Navigator's establishment at Sagres was not a 15th century NASA, and the Portuguese caravel was not a nautical revolution (though it was developed amid an ongoing revolution in nautical technology). In fact the lateen-rigged caravel turned out to be a bit of a technological dead end that faded away in the 16th century.
Christopher Columbus was just trying to go one better on the Portuguese, armed with a gross underestimate for the size of the Earth and sublime ignorance that there was a continent in the way. Unlike the great treasure junks the caravels were small, perhaps 20 meters long and 50 tons capacity - about a third the length and a thirtieth the displacement of their Chinese contemporaries.
China had perhaps 50 times the resources of Portugal. Sending out a few hundred men aboard a squadron of caravels was as heavy a burden on Portugal as sending 30,000 men aboard a treasure fleet was for China.
Why did Portugal's program of exploration succeed, while China's was cancelled and forgotten? The reason can't be things like decentralization versus centralization or government versus private initiative. Both were more or less the same on those counts, pushed by government factions and supported by the merchants, shipbuilders, and such who benefited.
There are no doubt a host of other factors. The Chinese court eunuchs had domestic rivals who wanted to cut them down to size, while Henry the Navigator was a royal younger son who seemed out to make none of the trouble that royal younger sons can make.
But I believe the more important reason is that the Chinese treasure fleets had absolutely nothing to do with broader Chinese concerns of the time. The Indian Ocean produced nothing that the Chinese wanted the way Europeans wanted pepper, and it was irrelevant to the empire's security concerns. (Whereas central Asia was all too relevant.) Seafaring itself was incidental to most of China's population.
It was much different with Portugal, a small country with a substantial fishing population that would readily go to sea for anything more profitable. More important, Portugal shared the reconquista heritage and crusading enthusiasm of neighboring Castile, and shared with much of Western Europe a late medieval fascination with knighthood and quests that gave us Sir Thomas Malory's Le Mort d'Arthur.
What is needed ?
* you need enough economy to afford the effort of colonization
* you need to have good enough ships and technology to do it
* you need to have the will (right attitude) in the people involved in the projects to do it
* you need a good enough business plan to get worthwhile products (spice or silver or furs) or modern services (satellite television, communications)
Just because you can do it, does not mean that you will do it.
China could have colonized America easily but did not.
So you have to have the initial conditions of basic affordability and sufficient technology and some kind of workable and sustainable plan. Then you need the people and groups who are willing to put it all together and actually do it.