Any time you study a particular topic you run the risk of skewing its significance. What is central to your thinking must be central to the author you are studying, right? In my study of Luke's understanding of the law of Moses, it has been helpful to step back far enough to notice that although law is important to the narrative argument of Acts, it pales in significance to faith. Consider the following evidence about Jewish Christ-believers and the law:
The early Jewish Jesus movement can be designated as "all those who believe" (Acts 2:44), the "multitude of those who believed" (4:32) or simply as "believers" (5:14). Jewish priests who respond become "obedient to the faith" (6:7), not the law. Both Jews and Gentiles who join the community are commanded to believe (16:31; cf. 10:43; 19:4; 20:21). By contrast, no passage in Acts enjoins Torah observance on Jews.
Law and faith need not be opposed, as they are in Paul, but this should be clear enough: In Acts faith is a positive requirement for all Christ-believers, while references to the Torah-observance of Jewish Christians are primarily descriptive.