I don't think there is a specific "firsts" lens one should buy. All depends on what one is going to take photos of most of the time. For example, the lens on a cellphone is an all purpose lens one can use most of the time. If one wants to use a camera that has a FF sensor, then you have to choose lenses that are appropriate for FF cameras, versus lenses for cameras with cropped sensors.
Lest say that you decide to buy a 50mm lens for your FF camera. In this case you may have to walk closer to the subject, or away from the subject if such subject is too large. But should you engage in macro photography, take into consideration that several camera and lens manufacturers offer 35mm to 100mm macro lenses. So you can buy a general use 35-50mm macro lens.
Camera manufacturers offer "kit" zoom lenses. These lenses usually are zooms one can use for most occasions. You will have to decided which first lens to buy taking into consideration the subject you are going to photograph most of the time.
Buying a first lens:
We know how overwhelming it is to find the right lens for you. Here’s a quick camera lens guide for choosing the right first lens to buy.
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Buying a second lens:
So you just bought your first interchangeable lens camera? Congratulations! Now it's time to add another lens to your arsenal. Read more
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This is what works for me:
a. For moose and other large animal in my backyard, I use a 100mm prime for the sharpest photos, or a 70mm-200mm zoom second.
b. For animals the size of a fox in my backyard using a cropped sensor camera, I use a 400mm prime. For the same animal using one of my FF cameras, I use a zoom lens out to 500mm, or just the same 400mm prime with a 1.4x extender, although most times I just crop the photo as needed.
c. For the local sled-dog races, regardless of camera used (FF or cropped sensor), my favorite lenses are (both Canon lenses): 135mm f/2 L, and 200mm f/2.8 L. However the new RF 100-500mm lens is quite sharp when mounted to the R5 or R6. In this case I zoom out to 300-340mm.
d. To photograph arctic ground squirrels I use the 200mm or 400mm primes above, mounted on the cropped sensor camera, or the same lenses "adapted" to the FF cameras (or just the RF 100-500mm lens on the FF camera).
e. For wide angle shots of the Northern Lights, I used a Tokina 14-28mm lens with the FF cameras.