You can add the plants right away. They can help with the cycle, if they come from an established tank (versus the ones you buy in the plastic tubes from the pet store). If you don't have all the plants yet just add them when you get them. It's really up to you. They may remove some of the ammonia from the tank but if you're doing a fishless cycle you are in control of how much ammonia is added, so it's not a big deal.
Just FYI - adding water conditioner will not help the tank start cycling - it simply makes the water safe for livestock (including the bacteria) by neutralizing chlorine and chloramines. You will need a source of ammonia for the cycle to start.