What three groups of people settled on the Italian peninsula?

Far more than three groups settled in the Italian peninsula. Ancient Italy was inhabited by the Umbrians, Sabines, Piceni, Aequi, Marsi, Maruccini, Paeligni, Frentani, Vestini, Samnites, Lucani, Dauni, Iapyges, Messapii, Campanians, Oenotrians, Ausoni, Aurunci, Sidicini, Latins, Faliscans, Etruscans, Ligurians, Gauls and Veneti.