Every dog has need of care of its coat. It makes of course a difference in time, if your dog has short hair or long, but every dog owner needs to take care of the coat.
Never use a shampoo for people with dogs: those shampoos are aggressive and can cause considerable damage. The skin of the dog contains a protective surface layer with glands, also the dog's skin is less acidic than the human skin. Use of a shampoo for people on a dog is absolutely not possible.
Therefore, a shampoo designed for use in humans are not good for use on a dog. There are many different types of special dog shampoos available, pay attention in making the choice that you order the right shampoo for your dog. There are differences: some shampoos are specially designed for black dogs, others for white dogs etcetera. There are also special shampoos for puppies and dogs with a sensitive skin.
Dogs do not, in principle, need to be washed with a shampoo often: 3 times a year on average. Still you need a good wash, i.e. if your dog smells less fresh or has become very dirty. It is important that you always rinse the dog after washing thoroughly, this will avoid possible skin irritation. For dogs that have a problem with the skin, you can best make a choice of the appropriate shampoos.