Answer:
Slave Trade
The British were very successful slave traders who transported millions of Africans to the Americas in exchange for raw materials. The income they received from this increased their coffers and made them capable to ruling an empire.
Second Agricultural and Industrial Revolution
The British were the first to introduce large scale changes to Agriculture that led to an increase in crop yields in what was termed the Second Agricultural Revolution. This led to them also taking the lead in Industry with the Industrial revolution.
They therefore had many new goods that were highly sought after in the world and so they established trading companies that sold these goods all over the world such as the British East India Trading company. These companies had military might and defeated entire kingdoms and subjugated them with the income they gained from trade.
The Royal Navy
There was a need to protect the trading routes of the British empire so the Royal Navy was expanded such that it became the foremost navy in the world and it remained that way for centuries until the emergence of the U.S. Navy.