积少成多

sand grains accumulate to make a tower a tower (idiom); by gathering small amounts one gets a huge quantity; many a mickle makes a muckle

lit. piling up dirt eventually creates a mountain (idiom); fig. success is the cumulation of lots of small actions

to accumulate tiny quantities (idiom)

to accumulate over a long period of time

many hairs make a fur coat (idiom); many small contributions add up to sth big; many a mickle makes a muckle

lit. thin streams flow forever; fig. economy will get you a long way