What is the cheapest website or way to travel domestically inside Canada , even i dont want to take luggages?

You can travel all day for a $10 transit pass in most cities.
Travel Agents make their living arranging cheap travel.
As you want to do it yourself you can spend your time looking for the CHEAP stuff.

Canoeing is cheap way to travel can go thousands of miles.
Walking riding a bike is cheap. Hitch hiking still happens but is not recommended anymore,not too many bus or train routes to pick from. ?The price is the price.
Grey Goose/Brewsters has value priced tours.

Canada Jetlines
Flair Airlines
Swoop
Air Transat.

For the cheap prices avoid travel June 20 to September 10.

All websites are free, unless you decide you want to buy something. Happy to help.

How far are you travelling? It's one thing to travel across a town or city and another thing to travel across the country.

That depends what places you are travelling between. Cheapest could be bus, train, plane or car. It won't be the same for every place. If more than one person is travelling, car can be very cheap especially if you already own the car

The cheapest way to travel inside Canada is called freight hopping.

It's extremely dangerous and completely illegal, but it's very cheap.

Drive your car.  

Long distance bus.

There really isn't one. Most places in Canada have very limited travel options.