They built churches (missions) in colonized lands, which were staffed by Catholic clergy, and in this way spread European religion as well as Spanish influence.
for spreading Christianity and gaining lands and getting gold
To search for gold and to establish its claim to the lands.
Spain got involved in exploration during the Age of Exploration in order to expand its territories, find new trade routes, and spread Christianity. Spanish explorers like Christopher Columbus, Ferdinand Magellan, and Hernán Cortés undertook expeditions to discover new lands and resources, establish colonies, and convert indigenous populations to Christianity. The Spanish crown saw exploration as a means to increase political power, wealth, and influence in the world.
They wanted to spread Chrstianity and conquer new lands.
The Arab Empire spread to all of Southwest Asia, Damascus, North Africa, Spain, and then eastward into the lands beyond Persia.
What lands did Spain claim
One word "Mercantilism"
The Age of Discovery saw an increase in ocean travel, which allowed churches to send representatives to distant lands to spread Christianity.
This was a time of imperialism, in which European countries fought for land and resources in other lands. This was the First Age of Imperialism, that included North and South America.
for the gold of the Americas
Missionaries, committed to the cause of either Christianity or Buddhism, spread the respective religions to other lands.
One reason Jesus came was to establish the Church of God on Earth as a place for the Firstfruits to gather and grow via the gift of God's Holy Spirit - the Comforter that Jesus promised. After His death, the Apostles and disciples spread this new message throughout the lands and soon afterwards, 'The Way' became known as Christianity - first coined in Antioch, Turkey.