Bart Ehrman argues in his most recent book, The Triumph of Christianity, that:
Nowhere in his letters does Paul indicate that he spent time in Jerusalem trying to convert anyone; on the contrary he makes it quite clear that he understood himself to be the missionary to the gentiles.
Maybe an evangelistic ministry in Jerusalem might not have been part of his ministry, however, I argue in An Anomalous Jew that Paul’s initial ministry was towards Jews (i.e., his time in Arabia and Damascus), then towards Jews and Gentiles (i.e., operating out of the Antiochene church), and then to Gentiles alone (i.e. his mission either side of the Aegean).
If you believe me not, then read Gal 1:15-18, Rom 1:16; 15:16; 1 Cor 9.20-23, Acts 9:3-6, 13-16; 22:17-21; 26:12-18.
The sources are ambiguous as to when Paul actually received his missionary call to go to the Gentiles. However, there is solid evidence coordinated between the Epistles and Acts which indicates that Paul’s time in Damascus, Arabia, and Jerusalem included preaching primarily if not exclusively to Judeans. It is in association with the Antioch church that Paul started to engage in missionary activity to Gentiles in Syria, Cyprus, and Asia, but always in the context of mixed Jewish synagogue communities. The capitulation of the church of Antioch to pressure from the Jerusalem church to adopt a model of proselytism as a basis for table-fellowship due to the rise of violent Judean nationalism resulted in a split between Paul and others with Paul retaining the “old Antioch” position. The subsequent result was that Paul focused more fully on Gentile converts and also attempted to socially insulate them from spheres of Jewish influence where they would not be pressured to judaize to the point of circumcision.In the later stages of Paul’s missionary work, where the call to the Gentiles finally worked itself out in mature form, Paul still saw the Jews as objects of his missionary preaching (1 Cor 9:20-23; 2 Cor 3:14-15, 4:3-6), he retained a belief in the necessity of a continued preaching mission to the Jews (Rom 10:14-21), and he knows of the church as made up of Jews and Gentiles who have been “called” and “believe” (1 Cor 1:24; Rom 9:24/Rom 1:16; 10:12-13).
I agree then with Martin Hengel: “It was never possible to draw a neat division between mission to the Gentiles and mission to the Jews in the church”.