J. Carleton Paget is quite right to state “In the beginning all Christianity was Jewish Christianity”. And even at the earliest stage there is evidence in Luke’s account that there were diverse groupings of Jewish Jesus-believers in Jerusalem, based especially on cultural background. Luke refers to what appears to be two main groups with the terms “Hebrews” (NIV: "Hebraic Jews") and “Hellenists” (NIV: "Grecian Jews") (Acts 6:1). These terms refer to the language and culture of the Jews in question. Those who were so-called “Hellentists” were Diaspora Israelites who had migrated back to Palestine in order to be in the Land and near the Temple. Presumably they were motivated by the desire to more wholly live a Torah-observant lifestyle. Whereas the Hebrews were native born Judeans and Aramaic speakers.
In the history of scholarship on early Christian history since Baur, these two groups have been assumed to be the earliest expression of the ideological divide within Christianity between those who believed in a Torah-free Gospel and those who didn’t, the Hellenists representing the former group and the Hebrews the latter. However, there is no foundation for this viewpoint as Bauckham and others have pointed out and what’s more it is likely that the Hellenists were even more zealous for the Torah than the Hebrews.
The implication of this first observation is that even at the earliest stage, when the only form of Christianity was Jewish Christianity, diversity existed. Later of course the diversity took a pronounced turn when the mission to the Gentiles got underway. At that point a new theological divide arose. It should be recognized that at the earliest stage the diversity was primarily cultural and did not have negative consequences of the later theological division. The problems between the groups seemed to be related to practical "pastoral care" issues--care of widows, etc. Moreover, this latter division did not form along cultural lines, but was the result of a difference in the interpretation of Torah and its application or non-application to Gentiles, a difference which it seems transcended issues of culture creating division even among Hebrews. Presumably the same is true for the Hellentistic Jews, although little evidence is either way is extant, save the Apostle Paul. There is no positive evidence that supports the oft-made claim that the Hellenists were primarily responsible for the Gentile mission after being scattered as a result of persecution (see Acts 8:1).
Carleton-Paget, James. 1999. Jewish Christianity. In The Cambridge History of Judaism: The Early Roman Period, ed. William Horbury, W. D. Davies and John Sturdy, 3:731-75. Cambridge: Cambridge University Press.
Hill, Craig C. 1992. Hellenists and Hebrews: Reappraising Division within the Earliest Church. Minneapolis: Fortress Press.