Which Nikon lense should I choose?

I have a Nikon D3100 and the main things I photograph are wildlife, (animals, flowers), knick-knacks, and clothing. Occasionally pictures at museums and exhibitions too. I'm deciding between the
Nikon Af-s 50mm F/1.8g Lens which has really good macro shots
and the Nikon Af-S DX 35 F1.8 which takes wider angle shots.

Which do you think would be more suited to my needs?

Neither would be any use for wildlife - not long enough. You need at least 200mm for that.

The 50mm is not a macro lens - it may have close focus capability but it is not a macro. May be too long for museums and exhibitions.

The 35mm will be good for exhibitions and museums as well as clothing and knick-knacks. So this covers most of your list.

None of the above. First, neither one is going to be of any use for photographing animals unless the animals are your pets. Second, the Nikon AF-S 50mm f1.8G is not a macro lens, Its closest focusing distance is about 1'-6'' and its reproduction ratio is about 1:5 which is 1/5 life size. A true macro lens will focus to within inches of your subject and has a 1:1 reproduction ration which is life-sized. Take a picture of a 20mm long ant with a true macro lens and it will be 20mm long on your sensor. With the AF-S 50mm your 20mm long ant would only be 4mm on your sensor.

On a 35mm film camera or full-frame DSLR like the Nikon D700 or D800 or D3 or D4 a focal length of 50mm is considered a "normal" lens since its angle of view approximates that of the human eye. On your D3100 the 50mm lens has the equivalent angle of view of a 75mm lens on a 35mm film camera or full-frame DSLR. This makes it a good choice for portraits.

On your D3100 the 35mm lens will have the equivalent angle of view of a 52.2mm lens on a 35mm film camera or full-frame DSLR. So on your camera it would be considered a "normal" lens and used when you want to capture a scene pretty much as you saw it.

So to fully meet your needs I'd recommend two lenses:

Nikkor AF-S 60mm f2.8G Micro (For some reason unknown to me Nikon calls their macro lenses micro. Go figure.)
Nikkor AF-S VR 55-200mm f4-5.6G IF ED

All zoom lenses are a series of compromises and the higher the zoom range the more compromises and the poorer the image quality. The 55-200mm has a 3.64x zoom range (200/55 = 3.64) while zoom lenses like, say, an 18-200 has an 11.11x zoom range (200/18 = 11.11). The very expensive Nikkor AF-S 70-200mm f2.8 zoom has a 2.9x zoom range. Care to guess which of these three lenses will have the best image quality? So in my opinion the 55-200mm will suit your needs without completely emptying your piggy bank.

The 50mm f/1.8 is not a macro lens. A macro lens would only go as far as f/2.8. F/1.8 however will be very useful in museums that allow cameras but no flash. For wildlife at a distance, you will need at least a 300mm lens. For most anything else, the 18-55mm kit lens will perfectly do.

http://keerok-photography.blogspot.com/2011/05/lenses-so-many-of-them-there-is-no-best.html