clipped from: digital-photography-school.com   
Travel-Photography-1

Weight

you probably will need to limit your lens choice to a couple of lenses simply because of the size and weight

Versatility

Depending upon your destination and the type of shots you take you’ll probably a lens (or combination of them) that is versatile and gives you a range of focal lengths

a lens that is as versatile as possible in terms of zoom size and speed can be well worth investing in

Lens Speed

The speed of a lens is signified by the number that usually appears after the ‘f’ on the lens (it’s aperture

The lower the number the more light the lens allows to hit your image sensor and the faster shutter speed you’ll be able to shoot at (ie the lower the number the faster the lens). When shooting in low light a fast lens is a real advantage

invest more into your lenses if possible as the improvements to photos are often made in this area

Having said that, just because you can’t afford a pro lens doesn’t mean you can’t take great shots