Shevuot 3: Sacrifices on a Sliding Scale

The Gemara's introduction to Shevuot seems far afield - in its sidestepping to tzara'at blemishes and Shabbat details. So it explains the connection to lashes in the previous tractate. Plus, the sacrificial offerings that are brought on a sliding scale - dependent on one's economic status. Plus, the period of lapsed awareness of one's status as impure (for example). Also, whose opinion is represented in the mishnah? The Gemara first explains that it is not in line with the opinions of either Rabbi Yishmael or Rabbi Akiva. Until it comes back around to Rabbi Yishmael.