I think go for Nikon 18-200 bro...Naa naman ka 50mm if you need bigger aperture during night ....but as per sa imo type of shooting nga landscape and travel mura duha gyud ni ka lens....If for me mag landscape/cityscapes ko mo go ko sa mas wider. Tokina 11-16 F/2.8 and Sigma/Nikon 24-70 F2.8? would be a good combination based on your style.