That could be a gang, a mob, or a troop.
Collection of coins is called collection of cons only n there is no specific word for it. It is different from numismatics as numismatics is the systematic study of coins. Mere collection of coins cannot be called as numismatics.
Audience (As in number of people listening to a radio broadcast)
At collection of stamps is refered to as a stamp collection. They are frequently kept in albums. Philately is the name for the study and collection of stamps.
A collection of people is often referred to as a "group." Depending on the context, it can also be called a "crowd," "gathering," "assembly," or "audience." The specific term may vary based on the size, purpose, or nature of the collection.
it is called a range of mountains
a collection of fish is called a school of fish
A collection of fish is called a school.
A collection of sayings is called a "proverb" or "aphorism."
A collection of opinions is called a "consensus" or a "survey."
A collection of pictures is called a gallery or an album.
A collection of rays is called a ray bundle.
Web page collection called a Website.