If you actually read Augustine you will see that his beliefs were VERRRRYYY different from Reformed beliefs. I do find it humorous that Reformed folks state they are carrying on the tradition of Augustine.
1) Augustine Believed in Purgatory and Praying for the Departed
2) Augustine Believed in the Necessity of the Lord's Supper for Salvation
3) Augustine Believed the Mass to be a Sacrifice
4) Augustine Believed in the Real Presence
5) Augustine Believed Baptism was Necessary for Salvation
6) Augustine believed in Baptismal Regeneration and Grace
7) Augustine Believed in Authoritative Tradition
8) Augustine believed the canon of Scripture to contain the Greek OT canon also known today as the deuterocanonicals or "Apocrypha"
9) Augustine Believed In the Communion of Saints and Saintly Intercession
10) Augustine Believed in the Authority of the Church
11) Augustine Believed in Apostolic Succession
12) Augustine Believed in the Possibility of Falling from Grace
13) Augustine Believed in the Sacrament of Penance
14) Augustine Believed Mary To Be Ever Virgin (of course so did Calvin...)

Grace is not common.