What lens should I use for wedding photography? (Nikon D3100)?

I have a Nikon D3100 and would like to get my feet wet in wedding photography (I would be doing this aside from a main photographer to gain experience… Wouldn't want to ruin their wedding day). I would like to know which lens I could purchase in order to do future group work/events/weddings. I plan on purchasing a 17-55mm f/2.8 but it is out of my price range for now. I have a budget of $650, and my current lenses include:

Nikon 18-55mm kit lens
Nikon 70-300mm f/4.5-5.6G ED IF AF-S VR
Nikon 35mm f/1.8G AF-S
Nikon 50mm f/1.8G AF-S

Thanks

Added (1). I forgot to add that I'm working with a Nikon SB-600 flash

The 50mm is a good lens. If it's indoors, you need a fast lens.

You generally want to stay longer than 35mm for any portraiture, wedding or otherwise due to the perspective distortion inherent in wide angle lenses.

A lot of pros have gone to a 70-200mm f/2.8 for wedding photography. Nikon's lens is pretty darned expensive, but Sigma makes one for about half the price - but it still ain't cheap.

That lens, along with a 50mm f/1.8 would be a good setup.

But any wedding photographer worth their salt will have a flash setup as well. While many times, the actual ceremony will not allow you to use a flash, the after-wedding photos almost always consist of a flash or three.

A single flash such as a SB700 and a Gary Fong Lightsphere would be a good setup as well.

www://www.althephoto.com

Don't use the 70-300 mm except maybe for some candid shots at the reception.

The 35 mm is too wide for portraits, but good for full body shots.

The 50 mm is a splendid portrait lens

The 18-55 mm is what you will use when shooting group shots.

Remember have your fee high enough to buy what you need as your business continues to grow. The lenses most used by wedding photographers are the 24-70 mm f/2.8, 50 mm f/1.4 or f/1.8 and 70-200 mm f/2.8