"A reader lives a thousand lives before he dies. The man who never reads lives only one." what does this mean help?

You live the stories you read.
If you don't read then your's is the only life you will know.

Each book that is read opens the mind to new worlds, new ideas, new possibilities, etc. A person who doesn't read doesn't see the world for all its possibilities.

presumably because you gain many perspectives by reading.

A reader will read many books during his/her lifetime. each one is an adventure. you can put yourself in harry potters shoes for example. or you can put yourself in katniss everdeens shoes and live her story. these are just two lives you can live, there are MANY more. One who doesn't read, doesn't experience this and only lives their own life. This is what this quote means.

I personally disagree since we have videogames and other ways to live imaginary lives.

The reader lives the lives of all the characters he's read about. A non-reader only lives his own life.

It's obvious. It's a copy of that quote, "A coward dies a thousand deaths, but a brave man only
dies once."
But for that quote it just means that the reader lives other lives vicariously through the books
he reads. It feels like he's living the lives of the people he's reading about. But the non-reader
only lives one life, his own life.

Twaddle.

It's a variation on the saying "A coward dies a thousand times before he dies. A brave man dies only once."
It means a reader has the opportunity of entering many lives through books while a non-reader doesn't.

those who tried out things will be more likely to succeed

Just what it says. I read Moby Dick and I live Ishmael's life for the duration of the book. I read Weird Dinosaurs and I live the life of the paleontologists that find and describe dinos. Very simple.