I want to buy a lens for my Nikon D3100 to take close ups, the cheapest one?

I would like to buy a lens for my Nikon D3100 to take close ups;this would be my first lens besides the one that comes with the kit. I'm a beginner, so I do not know much about lens.Preferably the cheapest one.

Not much info to go on here…

Just to avoid any misunderstanding… I'd send you in the direction of your local library, try reading through some of the photography guide books to get an idea of which lens would be your best bet… You might not get the answer your looking for… Keep looking until you find it,

It's not sensible to go cheap on a macro lens… Depending on what your shooting… It might be stuff you're selling on ebay or some wildlife like bugs and insects etc… If it's bugs and insect it's important to get the best focus… And a cheaper lens might not get you the best results.

fhotoace's suggestion is a cost-effective lens it isn't a cheap option… There's a difference… That's what you have to balance… And I reckon if you have to make compromises on kit then it's best to make an informed choice… Do lots of research and buy the best you can afford… Even if it's refurbished, used or second-hand… Just make sure the lens can do what you are expecting.

I use a 90mm macro lens and it's my favourite lens… It gives a decent distance to work with and gives consistent results.

The Nikkor AF-S 40 mm macro lens will do what you want and is the least expensive macro made by Nikon (or probably anyone else at $280)

Have you tried the close up mode first described on page 29 of your manual? You might get the results you want with your kit lens and close up mode.

The Nikon AF-S Micro-Nikkor 60mm f/2.8 has more working distance than the Nikon 40mm f/2.8G AF-S DX Micro-Nikkor and is a good portrait lens.
If you go and buy the 60mm for $547, it costs you $547.
If you go and buy the 40mm for $277, it costs you $277 plus the $547 you will spend to replace it with the 60mm.

Closeup portraits (head shots)? Your 18-55mm lens will do great at 55mm. If you want to blur backgrounds, just position the subject as far away from the background as possible and use the lowest f/number possible. Want to blur backgrounds more easily? See this.

http://www.bhphotovideo.com/..._50mm.html

Not that? Are you talking about making small objects seem large? You need a macro lens like this.

http://www.bhphotovideo.com/..._AF_S.html

Well you do not have a cheapo camera and given the lens is the most important part of a camera, you do not want to go looking for the cheapest lenses to fit. Stick with Nikkor lenses. Now there's one way to economize with a macro lens. If Nikon is like my camera (Pentax) there are probably at least two macro lenses available.
In my case there's a 100mm selling $850.00 and a 35mm selling at about half that. So if you are in good shape physically, I would go for the cheaper lens in THIS case. Personally I went with a USED 100mm @ $500 since I'm in my seventies and crawling around on the ground is difficult for me. With the 100mm I can photograph at a comfortable distance. If you have no such problem I would go with the "shorter" macro lens.
The $280 price that fotoace qouted sounds like just the ticket for your needs and budget!