I am planning to buy a d5100 with 18-105mm lenses.

I am planning to buy a d5100 with 18-105mm lens.
Do you have any suggestions for a second lens I can purchase? like for example a 50mm 1.8 prime lens?

Thanks!!

Stick with the 18-105mm lens for a while and get used to it before you buy anything else. Once you have it for a while you can then make a good decision on what you want.

The 18-105 covers quite a useful range, and with its 3.5-5.6 aperture, getting a fast lens for low light situations would be a good idea. It really depends on what you shoot. You might opt for a fast medium telephoto lens, or the 50 1.8 as you mention would be a good general purpose, compact fast lens. It also depends on your skill level as a photographer. If you are very new to photography, I would actually recommend working with the 50 mm first to get the basics down in terms of the photographic process, and then play with the zoom lens. The prime lens would also be for more serious photography were you want that bit of extra sharpness and punch to your images (with the subject jumping out of a soft bokeh background). If you shoot people a lot, you might opt for a fast 85, 105, 135, or 180 mm lens. If you do a lot of interior shooting, then a fast 28, 24, or 20 mm lens might be a good second choice. So it really depends on the demands of what you are shooting....

This is the same rig that I have (D5100 with 18-105) . I also have the 55-300 lens and have hardly use it.

That's the setup I'm using right now (D5100, 18-105) and I'm finding the 18-105 covers probably 80% of what I shoot. The 18-105 is the lens I wish I'd had from day one and I think you'll find it's a great place to start. The other lens I wouldn't be without is my 35mm f1.8 prime, mainly for low light/speed. Yes, I do *have* other lenses but those two are my "right and left hands". The 18-105 rarely comes off my camera unless I'm switching to the aforementioned 35mm.