Complex sentence: While they were initially unsuccessful, the band built a dedicated fan base through extensive touring, word-of-mouth and Internet promotion; "Adrenaline" also went on to sell over 220,000 copies.
Split into simpler sentences: While they were initially unsuccessful, the band built a dedicated fan base through extensive touring, word-of-mouth and Internet promotion. Through their efforts, "Adrenaline" went on to sell over 220,000 copies.