The most influential minority groups in ancient China were the famous Xiongnu and Xianbei nomad tribes.
Later, it was the Mongols and the Manchus that made the most impact.
There is however no doubt that the large number of minority groups have made China into a true melting pot of ethnicity over at least four millennia.
Even before the two prominent Chinese empires of Yuan and Qing were established by the minorities in China, there were the Liao kingdom established by the Khitan, the Jin kingdom established by the Tungusic Jurchen, the Tibetian empire of the Tibetans/Qiang, the Nanzhao kingdom of the Yi and Qiang, and the Xixia empire of the Tangut.
All these played major roles in the integration of the diverse ethnicity in China into what China is today.