Could you tell us about the first Islamic group and its role in spreading Islam?

A Muslim should not preoccupy himself with asking about deviant sects, as no legal ruling is dependent on it. Rather, he should focus on what Allah has made obligatory and what He has forbidden. If he wishes to inquire, let him ask about the characteristics of the victorious group. Among the most important characteristics of the people of truth are:

Following the Quran and Sunnah, abandoning innovation, adhering to what has been reported from the Companions, striving for unity and shunning discord, believing in Allah's attributes without distortion, denial, anthropomorphism, or resemblance, and believing that the Companions are the best of the Ummah after the Messenger, while refraining from discussing their disputes.

Whoever follows the methodology of the people of truth and strives to convey it is a true caller to Islam.