Answer by taking a quote from the following article:

Stephen Ray Vaughan (October 3, 1954 - August 27, 1990) was an American musician, singer, songwriter, and record producer. In spite of a short-lived mainstream career spanning seven years, he was one of the most influential guitarists in the revival of blues in the 1980s. AllMusic describes him as "a rocking powerhouse of a guitarist who gave blues a burst of momentum in the '80s, with influence still felt long after his tragic death." Born and raised in Dallas, Texas, Vaughan began playing guitar at the age of seven, inspired by his older brother Jimmie.

In May 1969, after leaving the Brooklyn Underground, Vaughan joined a band called the Southern Distributor. He had learned The Yardbirds' "Jeff's Boogie" and played the song at the audition. Mike Steinbach, the group's drummer, commented: "The kid was fourteen. We auditioned him on 'Jeff's Boogie,' really fast instrumental guitar, and he played it note for note." Although they played pop rock covers, Vaughan conveyed his interest in the addition of blues songs to the group's repertoire; he was told that he wouldn't earn a living playing blues music and the band parted ways. Later that year, bassist Tommy Shannon walked into a Dallas club and heard Vaughan playing guitar. Fascinated by the skillful playing, which he described as "incredible even then", Shannon borrowed a bass guitar and the two jammed. Within a few years, they began performing together in a band called Krackerjack.  In February 1970, Vaughan joined a band called Liberation, which was a nine-piece group with a horn section. Having spent the past month briefly playing bass with Jimmie in Texas Storm, he had originally auditioned as bassist. Impressed by Vaughan's guitar playing, Scott Phares, the group's original guitarist, modestly became the bassist. In mid-1970, they performed at the Adolphus Hotel in downtown Dallas, where ZZ Top asked them to perform. During Liberation's break, Vaughan jammed with ZZ Top on the Nightcaps song "Thunderbird". Phares later described the performance: "They tore the house down. It was awesome. It was one of those magical evenings. Stevie fit in like a glove on a hand."  Attending Justin F. Kimball High School during the early 1970s, Vaughan's late-night gigs contributed to his neglect in his studies, including music theory; he would often sleep during class. His musical career pursuit was disapproved by many of the school's administrators, but he was also encouraged by many people to strive for a career in art, including his art teacher. In his sophomore year, he attended an evening class for experimental art at Southern Methodist University, but bailed when it conflicted with rehearsal. Vaughan later spoke of his dislike of the school and stated that he had to receive a daily note from the principal about his grooming.

What was his biggest success in the early years?
perform. During Liberation's break, Vaughan jammed with ZZ Top on the Nightcaps song "Thunderbird".