Frank Collett, from Gloucester, admitted five charges of sexual activity with a child under 16 when he appeared at Gloucester Crown Court.
Collett, 24, groomed three girls aged 15 and a 13-year-old on social media.
He was jailed for four years and six months and placed on the sex offenders register for life.
The court was told Collett was fully aware of the age of his victims.
Judge Michael Cullum said he had preyed on the "vulnerability and immaturity" of the teenagers.
"Your last victim, troublingly, was just 13 and you knew that was even more wrong than the other.
"I have no doubt you were grooming her for further sexual activity," he added.
The mother of one of one victim, a girl described as having special needs, said Collett was "vile and disgusting".
She added that it had taken her daughter "a long time to realise it wasn't her fault".
Det Con Tess Nawaz said Collett would contact girls on social media and it was quickly clear the contact had a "sexual purpose".
She added that it had been a "very difficult time for the families".
Collett was also given a sexual harm prevention order for ten years, which prevents him from making any contact with anyone under the age of 16 or contacting the victims in the case.
A man jailed for grooming four vulnerable teenage girls for sex has been described as "vile and disgusting" by the mother of one of his victims.