Circumcision starts with Abraham. It is only in the series of covenants with the Jews.
Genesis 17:10 (NIV2011)
10 This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall be circumcised.
As for Gentiles,
Romans 2:14-15 (NIV2011)
14 (Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law.
15 They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them.)
Romans 3:1 (NIV2011)
1 What advantage, then, is there in being a Jew, or what value is there in circumcision?
Roman 2:17 - Roman 3:8 are about how the Jews should do about the Law (Mosaic Law) and circumcision.
Genesis 17:10 (NIV2011)
10 This is my covenant with you and your descendants after you, the covenant you are to keep: Every male among you shall be circumcised.
As for Gentiles,
Romans 2:14-15 (NIV2011)
14 (Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law.
15 They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them.)
Romans 3:1 (NIV2011)
1 What advantage, then, is there in being a Jew, or what value is there in circumcision?
Roman 2:17 - Roman 3:8 are about how the Jews should do about the Law (Mosaic Law) and circumcision.