There are many ways to describe a person who collects things. They can be called a hoarder, a magpie, a gatherer, finder, or a hobbyist.
A person who collects things is typically called a "collector" or a "collector specialist."
A person who collects comic books is called a comic book collector or a comic book enthusiast.
A person who collects nests or eggs and studies them is called an oologist.
Bibliophile
leaves collector
A person who collects coins is called a numismatist.
Someone who collects everything would be called a hoarder - this type of person may have OCD as well.
People that do this are called "rockhounds".
A Statition.
A philatelist is a person who collects stamps.
A news reporter
A phillumenist. The hobby is called phillumeny or phillumenism.