There are two common quotes in photography:
The best lens you have is your feet
The best camera you have is the one with you
These are both great arguments for buying and using 50mm lenses.
50mm lenses will encourage you to move around and get creative because you don’t have the option of a zoom lens. Without simply being able to zoom in or out on your subject you will start to move. Moving will have a few benefits to your photography. One of the major ones is you will start to explore your subject. It is very easy to get in the habit with cellphones and zoom lenses to only shoot subjects straight on at eyelevel. Most subjects have been photographed straight on at eye level thousands of times you will not get a good photograph this way, at best you will take a “technically good” photograph that no one will ever bother to look at twice.
So to repeat 50mm lenses will get you moving this will make you explore your subject and take shots from more interesting angles.
How will a 50mm make help you with have your camera with you? 50mm lenses are small, not only are they small 50mm lenses are cheap. This is not to say they are low quality, in fact even cheap 50mm lenses are some of the high-quality (in terms of IQ) lenses on the market. They are cheap and high quality because they require less glass than super wide angles, zooms or telephotos and they have been pretty much the same designs since the 80’s.
Basically 50mm are small, cheap high-quality lenses that will get you using your feet and carrying your camera.
But there is another advantage to 50mm lenses especially for people just starting to use a DSLR. 50mm are the cheapest lenses with very fast apertures there are many advantages to a fast aperture but for a starting photographer the biggest advantage will be that you will actually see bokeh( the artistic blurring of the background caused by large apertures) in their photos and will be able to see the difference in the amount of light being let in. Being able to see and feel the affect of aperture on your exposure and in your composition is a huge advantage that most kit lenses simply don’t offer.