I have a nikon d3000 what lenses are good to buy?

I want to take pictures of scenery mostly

If you have the 18-55mm, concentrate on learning how to use it.

Landscapes (scenery) photographs can be shot using your 18-55 mm lens at 18 mm.

If you want mind blowing landscapes, you are going to have to look at some super wide angle lenses like the Nikkor 12-24 mm and 10-24 mm or the Tokina 11-16 mm or 12-28 mm. All of them are rather expensive, so while you practice with your 18-55 mm, start saving your pennies. The Tokina lenses are excellent and cost a bit less than the Nikkor lenses.

Visit the websites of both to see what other options you have.

http://www.nikonusa.com/...index.page

http://www.tokinalens.com/tokina/products/atxpro/