I agree -- good start. With landscape photos, when there's a visible horizon, make sure to keep it absolutely level, and give some thought to where it lies in the photo (composition). Typically, you'll want to move the horizon away from dead-center. In all three of these shots, the sky is a supporting element, so I'd compose with a little more landscape and a little less sky.
In addition to mastering the technical aspects of exposure, effective tripod shooting, and so on, great landscapes demand great composition, so be sure to experiment with different focal lengths and look for elements at different distances to help create a sense of dimension. That second photo, for instance, would benefit from composition that uses that river to draw the viewers' eyes through the landscape out to the horizon. Sometimes, the inclusion of some foreground interest can help create a path to lead the eyes out toward the vista in the distance as well. Check out some of the landscape photography on 500px and see if you can spot some of those elements of composition.
Keep up the good work.