Berries 1-16 are 60 power. Berry 1 is Fire type, Berry 2 is Water
type and so on. Berry 16 is Steel type.
Berries 17-32 are 70 power. Berry 17 is Fire type, Berry 18 is Water
type and so on. Berry 32 is Steel type.
Berries 33-35 are 80 power. Berry 33 is Fire type, Berry 34 is Water
type and Berry 35 is Electric type.
Berries 36-52 are 60 power. These are the type damage reduction
berries. Their type is the same as the type of damage they reduce.
Berry 52 is the only berry that does Normal type damage.
Berries 53-60 are 80 power. Berry 53 is Grass type, Berry 54 is Ice
type and so on. Berry 60 is Bug type.
Berry 61-64 still have an unknown effect. Note that there are five
types left to complete the 80 power set, but only four berries left.
[Berry Number List for reference]
"Natural Gift inflicts damage and has no secondary effect. Natural Gift's power and type vary depending on the user's held Berry. Using Natural Gift consumes the held Berry"
as stated by *Bulbapedia*
Say you wanted a grass move on your Ninjask to get rid of those pesky Swamperts that keep using Roar and switching you out when you try to set up. You could give it berry that gives Natural Power a grass type and then KO those Swamperts
Basically, it's only useful when surprising opponents
Hope it makes sense