Will you have a car or not?
You will arrive in downtown Vancouver at either Canada Place or Ballantyne Pier.
No car: You would have to get to Pacific Central Station on skytrain from nearby Waterfront Station (10 minutes) to take Pacific Coach Lines to the ferry, on the ferry, and continuing on south down to Victoria. This journey takes 4 hours downtown to downtown. You do not have to make ferry reservations as you would be on the coach.
Cost? coach + ferry fares = $52.50
With car: You would have to get to your rental car office and rent your car, maybe up to an hour, then drive from downtown Vancouver to downtown Victoria, including the ferry. This journey takes 4 hours plus any time it takes to rent the car.
Do you need a reservation? I cannot advise without knowing the date and day of the week.
Cost? car + passengers = $51.25 plus $15.50 per passenger
Map for this route: http://goo.gl/maps/4b5FD
For future reference, it is usually a good idea to ask your new question by clicking on the "Ask a Question" button. It can be found on this thread under my post and below the reply box. Or it can be found on the main page of topics listings just above the list toward the right.