not sure if you've sorted what lens you want yet, if not perhaps I can offer a little advice
if your taking landscapes, then the kit lens can do a great job, as you will have the aperture to about F11 to F16 (to capture the distance and foreground in focus), then you are not worried about having a fast expensive lens, my advice would be (assuming you ahve the canon 17-55 or 18-55) lens is to use that and if you dont have a good tripod and a remote release, invest in those, as they will improve your landscape images a lot more than a lens, I had a cheap tripod and used a collegues quality tripod and the difference in the pictures was astounding
Phil