You only need to really bathe a dog once per month or once every few months unless the dog gets messy or dirty and really needs a bath.
Bathing your dog too often can dry out the dogs skin and cause the dogs coat to loose it's shine so it's not recommended to bathe the dog anymore often than once per month or once every 2 months.
That is unless like I said the dog gets dirty and needs a bath then it's okay to give the dog a bath more often.
Bathing the dog too often can remove the natural oils on the dogs skin which dries out the skin so only bathe the dog when needed.
Dogs will sometimes lick their fur and skin to help keep themselves clean as well so there's no need to always constantly bathe the dog.