Ships.
Sea transportation was just right at that time as it can carry loots, spoils of war , enough fire power to conquer new colonies, and also food and necessities for sojourners ,seafaring soldiers and traders. Even exploration of unknown territories was also done with the help of sea transportation.
Victory over the Persians, defeat by Sparta began the golden age. It ended due to the Peloponnesian War.
At the First Continental Congress, the delegates discussed boycotting British goods all together, but decided to send the Crown a list of their grievances in the hopes of getting the Intolerable Acts lifted.
It gave them more power because before they didn't have much power.